D -   ability = can do

1-C   assignment = homework

2- B    replaced = changed to

1- A     reading material = books

2- B      negative effect = bad result

3-B       enjoyable way  = pleasant way

1-B,   2-A,  3-C

Correction.

Possessive pronouns

...., theirs is bigger and ours is smaller.

They are Possevive pronouns.

1-B

2-D

3-B