wireless services, modifiers

[tnaim]

As the cost of wireless service has steadily dropped over the last year and as mobile phones have become increasingly common, many people are finding that they can avoid toll charges on their home phones, using their mobile phones for making long-distance calls at night or on weekends, at a time which many wireless companies provide unlimited airtime for a small monthly fee
a) same as above
b) phones, instead using mobile phones to make long-distance calls during the night of weekends, during which
c) phones by using their mobile phones to make long-distance calls at night or on weekends, when
d) phones using mobile phones for making long-distance calls during the night or weekends, when
e) phones when using their mobile phones to make long-distance calls at night or on weekends, a time which.

My question is not about the answer to the underlined part, but rather about the structure: as the cost of wireless....., many people are finding that..

This structure must be correct but it seems to me that the first part of the sentence (as the cost of wireless service has steadily dropped over the last year) modifies (many people) which wouldn't make sense. I thought a more appropriate way would be (and again I'm not correcting GMAT official guide here, I'm just trying to find out what I'm doing wrong): as the cost of wireless service has steadily dropped over the last year and as mobile phones have become increasingly common, home phone charges are easily avoided.......(here the charges are modified by the first part of the sentence which makes more sense).
Would you please help me understand what it is I am assuming wrong? is my understanding of the structure correct? is the first part a modifier? if yes, am I right to assume that it should modify phone charges?
thanks in advance

[kevincanspain]

As <clause> is not a modifying phrase: as could be replaced by since or because

As I could not go to the supermarket yesterday, my children had to eat breakfast cereal for dinner


However, we write

As head of the zoning committee, Irene rejected hundreds of applications...

[tnaim]

As <clause> is not a modifying phrase: as could be replaced by since or because

As I could not go to the supermarket yesterday, my children had to eat breakfast cereal for dinner


However, we write

As head of the zoning committee, Irene rejected hundreds of applications...

Thank you Kevin,
Can I take it then as a rule of thumb that modifying phrases can only be of three types:
1)gerund (ing + verb): counting on his presence, she was confident about...
2) past participle adjectives (ed): delighted by the team's peformance, the coach thanked the team members.
3) infinitive: (to hold): to ensure participation in the game, she fulfilled all the of the requirements 3 months before competition started.

[ansumania]

now 'll you please provide the OA?

[frank1]

I think its C

[frank1]

double post:edited

[debmalya_dutta]

I too think its C

However , after having a look at kevincanspain's comment , I think the over-all structure of the sentence is wrong
It shouldn't start with "As" but should have started with Because. I would avoid since too though it sounds right

[tnaim]

now 'll you please provide the OA?

Sorry forgot to post the OA which is C

[rameshmbaprep]

The OG says that not using "by" is the problem with option D. Can anyone please explain, what the sentence would mean without "by". And also is the usage of "for making" not a problem in option D?

[saketk]

I saw my friends, talking to each of them. ( I TALKED to each of my friends)

Well I am not sure whether this sentence is grammatically correct.

Also, it surely does not clearly conveys your intended meaning.

If you want to say - you were talking to each of your friends then the better sentence is ..

I was talking to my friends.

If you want to say -- 'you saw your friends while they were talking to each other' then you need to re-structure your sentence.

[mankey]

Can I take it then as a rule of thumb that modifying phrases can only be of three types:
1)gerund (ing + verb): counting on his presence, she was confident about...
2) past participle adjectives (ed): delighted by the team's peformance, the coach thanked the team members.
3) infinitive: (to hold): to ensure participation in the game, she fulfilled all the of the requirements 3 months before competition started.

The poster has put forward a great question. Can some expert please respond to this? This is more about the fundamentals, then just this question.

Will really appreciate.

Thanks.