31 is "the incorrect use of subject verb agreement"
Oh ok. Can you help me with some of the others? I'm having a really hard time with this for some reason. :/
The subject is "materials" and "is" is the verb. Since "materials" is plural, the verb "are" is appropriate.
I know 32 is wrong because was should be were, right?
Is anything wrong with 33? I cant find anything.
33 and 34 are correct.
The rest I'm uncertain of... some look incorrect but I can't pinpoint what is wrong with them.
I think so too