Fill in the blanks. The class is nervous about _____ first exam.
A. its'
B. its
C. it's
D. they're
In the given sentence, "the class" is a singular noun and requires a singular possessive pronoun. "Its" is the correct form of the possessive pronoun "it" to use with a singular noun, as opposed to "it's," which is a contraction of "it is" and would not be appropriate in this context. "They're" is a contraction of "they are" and would not be appropriate because "class" is singular, not plural.
Therefore, the Correct Answer is B.