Shoes, pants, scissors, glasses,etc. are combined with pair.
A pair of shoes, a pair of pants, a pair of scissors, a pair of glasses...
All I know about agreement related to pair is following.
Shoes are...
A pair of shoes is...
Two pairs of shoes are...
This pair of shoes is...
These pairs of shoes are...
When I saw the question below, I was quite puzzled because I'd never puzzled over this kind of matter. Help me, please.
Question>
_____ small for my son.
a) These pairs of shoes look
s 
b) This pair
s of shoes looks

c) These pair(
s) of shoes look

d) This pair of shoes look
s 