Ron,

I read the explanations again and again & reached the following conclusion. Please correct me if I'm wrong.

What I gather from all of the explanations above, the following ones are correct:
I have never seen an aardvark, but last year my father did.
--> Helping verb changes tense but this is right.
I have never seen what my father did.
--> Now, this sentence would be wrong because it says: I never got to see what my father executed.
I have never seen an aardvark, but next year I may do.
--> wrong, because no two helping verbs are used together in this respect
I have never seen more aardvarks than I did last year.
--> this is also fine for the same reason that helping verbs can change tenses as long as there's no change in the meaning e.g. I have never seen what my father did
thanks in advance.

lunarpower wrote:

magic monkey wrote:I have never seen an aardvark, but last year my father saw one.
I have never seen an aardvark, but last year my father did.
I have never seen an aardvark, but next year I may see one.
I have never seen an aardvark, but next year I may do.
I have never seen more aardvarks than I saw last year.
I have never seen more aardvarks than I did last year.

all of these are fine except the fourth one. that one is incorrect because it contains two consecutive helping verbs ("may" and "do"); you can't use more than one helping verb.

divineacclivity wrote:Ron,

I read the explanations again and again & reached the following conclusion. Please correct me if I'm wrong.

What I gather from all of the explanations above, the following ones are correct:
I have never seen an aardvark, but last year my father did.
--> Helping verb changes tense but this is right.
I have never seen what my father did.
--> Now, this sentence would be wrong because it says: I never got to see what my father executed.
I have never seen an aardvark, but next year I may do.
--> wrong, because no two helping verbs are used together in this respect
I have never seen more aardvarks than I did last year.
--> this is also fine for the same reason that helping verbs can change tenses as long as there's no change in the meaning e.g. I have never seen what my father did
thanks in advance.

lunarpower wrote:

magic monkey wrote:I have never seen an aardvark, but last year my father saw one.
I have never seen an aardvark, but last year my father did.
I have never seen an aardvark, but next year I may see one.
I have never seen an aardvark, but next year I may do.
I have never seen more aardvarks than I saw last year.
I have never seen more aardvarks than I did last year.

all of these are fine except the fourth one. that one is incorrect because it contains two consecutive helping verbs ("may" and "do"); you can't use more than one helping verb.

Hi divine,

As far as I know, all of your conclusions are correct except this,

I have never seen what my father did.
--> Now, this sentence would be wrong because it says: I never got to see what my father executed.

Just technically speaking, it is a reasonable sentence that makes sense, literally meaning WHAT MY FATHER DID.

Well it is ok, but it will not mean "father saw ..."

lunarpower wrote:

I have never seen an aardvark, but next year I may do.
--> wrong, because no two helping verbs are used together in this respect

Yes.

I have never seen more aardvarks than I did last year.
--> this is also fine for the same reason that helping verbs can change tenses as long as there's no change in the meaning e.g. I have never seen what my father did
thanks in advance.

Correct conclusion, but incorrect analysis. "Did" is just referring to a tense of "see" again (as in the first example above).

It seems the 6th Mgmat guide still believe the tense between the verb and helping verb should match.
Quite strange...