i think the answer is d. we cannot conclude 1 and 3.
III) If it had been manufactured a year later, my computer would have had a faster processing speed.
from the statement, we do not know which year the person's computer was manufactured. the statement 3 is true only if the comp was manufactured in 98. what if it was manufctrd in 87?
what is the answer?

Ans should definetely be D i.e I AND III

Am i mis understanding the phrase " Which of the following can definitely NOT be concluded from the above statements"..... My understanding of this is that, if i can see if the option is definitely wrong or correct : that means I CAN conclude. If i am not sure of the answer is right or wrong, I CANT conclude ....

So

I) My computer was definitely manufactured after 1998 --> surely wrong . Hence I CAN conclude this is not the right answer.

II) My computer may have been manufactured in 1998 --> this may be true / may not be true. Hence I CANNOT conclude the answer

III) If it had been manufactured a year later, my computer would have had a faster processing speed. Surely wrong . Hence I CAN conclude this is not the right answer.

Hence I choose option B.

OG is D