OFFICIAL EXPLANATION
From May 23, 2008, visitors to the San Diego Zoo can buy nutritious biscuits that giraffes can eat and participate in their feeding sessions.A. to the San Diego Zoo can buy nutritious biscuits that giraffes can eat and participate in their feeding sessions
This answer choice is ambiguous, that is, stylistically flawed. The pronoun their is ambiguous as it could refer to visitors or giraffes.
What helps us identify this question as a Pronoun question as well as identify the ambiguity mistake is the following Stop Sign:
Every pronoun in the underlined part of the sentence or after it
B. to the San Diego Zoo can buy nutritious biscuits that a giraffe can eat and participate in their feeding sessions
This answer choice is grammatically incorrect. The plural pronoun their does not agree in number with the singular noun to which it refers (a giraffe).C. to the San Diego Zoo buy nutritious biscuits that giraffes can eat and participate in their feeding sessions
This answer choice repeats the original ambiguity mistake and is thus stylistically flawed: the pronoun their is ambiguous as it could refer to visitors or giraffes.
What helps us identify this question as a Pronoun question as well as identify the ambiguity mistake is the following Stop Sign:
Every pronoun in the underlined part of the sentence or after it
In addition, the omission of the verb can changes the meaning of the original sentence.D. to the San Diego Zoo can buy nutritious biscuits that giraffes can eat and participate in the giraffes' feeding sessions
By adding giraffes' feeding sessions it is clear whose sessions are being referred to.E. to the San Diego Zoo buy nutritious biscuits that giraffes can eat and participate in the giraffes' feeding sessions
While this answer choice corrects the original ambiguity mistake, it changes the meaning of the original sentence by omitting the verb can.