3. David had been a great tennis champion in his youth, but decided to change professions in adulthood and began a small business selling tennis equipment, which, to this day, he still runs.

1. decided to change professions in adulthood and began a small business selling tennis equipment, which, to this day, he still runs.
   
   
2. had decided to change professions in adulthood and began a small business selling tennis equipment, which, to this day, he still runs.
   
   
3. decided change professions in adulthood and had begun a small business selling tennis equipment, which, to this day, he still runs.
   
   
4. decided to change professions in adulthood and began a small business selling tennis equipment, which, to this day, he still ran.
   
   
5. had decided to be changing professions in adulthood and began a small business selling tennis equipment, which, to this day, he still runs.

 
David had been a great tennis champion in his youth, but decided to change professions in adulthood and began a small business selling tennis equipment, which, to this day, he still runs.

Grammar issue presented: verb tense

-          The sentence describes a sequence of events in David's life. He started as a tennis champion, then chose to run a small business and continues to do so today.

-          Therefore, each stage of his life must be in the appropriate tense to fit the time sequence.

The sentence is correct as it is:

David had been a great tennis champion in his youth,

Tense: Past Perfect:

describes the first event in David's life, which occurred prior to other events in the past.

but decided to change professions in adulthood and

Tense: Past:

describes second event in the past, which happened next.

 began a small business selling tennis equipment, which,

Tense: Past

describes the result of David's decision

to this day, he still runs.

Tense: Present:

describes what David does now.

1. decided to change professions in adulthood and began a small business selling tennis equipment, which, to this day, he still runs.
   Tense: past perfect, past, past, present
   Correct: YES

2. had decided to change professions in adulthood and began a small business selling tennis equipment, which, to this day, he still runs.
   Tense: past perfect, past perfect, past, present
   Correct: NO
   Had been a great tennis champion and had decided to change professions both use past perfect. It appears that David was a great tennis champion at the same time he decided to change professions. 

3. decided change professions in adulthood and had begun a small business selling tennis equipment, which, to this day, he still runs.
   Tense: past perfect, past, past perfect, present
   Correct: NO
   Had begun should not be in the past perfect – because David's small business venture happens after his tennis champion days and after his decision to change careers.  

4. decided to change professions in adulthood and began a small business selling tennis equipment, which, to this day, he still ran.
   Tense: past perfect, past, past, past.
   Correct: NO
   He still ran makes it seem that David stopped running his business.  Therefore the phrase to this day makes no sense.

5. had decided to be changing professions in adulthood and began a small business selling tennis equipment, which, to this day, he still runs.
   Tense: past perfect, past perfect progressive, past, present
   Correct: NO
   Had decided to be changing makes the sentence unclear. The timing is confusing and vague, so this is not the best choice.

(A) uses the proper tenses to convey the correct timeline, and is thus the best choice.

Q.3 Hard

Q.4 Hard