Which type of punctuation marks are usually used to enclose letters or numbers that precede items in a list?

a. commas
b. parentheses
c. colons
d. periods

the autor of the text is bringing the point that one achievment of the president john f. kennedy was a success and this caused the next president to use a similar idea. the purposefor the use of the quotation in the text is to support the idea that peace corps was a result of the president's call. in this case, the quotation is presented as part of the writing and does not stand on its own.

answer a.