The answer would be a. Yes, the student’s answer is
reasonable.
In the problem, it states that Cindy rode her bike for an
hour and ran for an hour. Without the
presence of the comma between rode her bike for an hour, and ran for an hour,
this just means that Cindy only rode her bike and ran it for an hour.
The sentence can be written as Cindy rode her bike and ran
for an hour. So, this gives an answer
that Cindy only exercise for an hour.
