Here is another set of two question's.
--------------------------------------------------------------------------------------------------------------
Which sentence does not contain any errors in comma usage?

A.
That house, which has been for sale for six months is one hundred years old.

B.
Candles which can provide light at night, are made from different kinds of wax.

C.
The book, that you are looking for, is right here.

D.
The car that he drove on the muddy road will need to be washed.
---------------------------------------------------------------------------------------

Which sentence does not contain any errors in comma usage?

A.
Pam is singing with the woman, who wears fancy gowns all the time.

B.
There is the girl, who will sell the tickets for our raffle.

C.
Mom is the person, who can help with that math problem.

D.
Dad is someone who knows how to read quickly.

For the first question you have to use that tip that i've reminded you ;) answer variant C because ' that you are looking for ' it's the developed appositive which is isolated through that pair of commas ;)

For the second one the answer is variant D because it's no need of the usage of commas in the sentence. Variants A,B,C use the same rule for comma which is the wrong one.

Answer Link