Which sentence demonstrates correct subject-verb agreement?
a. dave wiens, a denver native and champion mountain biker, design the olympic mountain bike course in atlanta, georgia.
b. exploring international mountain passes, such as those in new zealand, canada, and japan, are one of the biker’s favorite hobbies.
c. wiens’s competitors, such as john tomac and mike kloser, inspires him to train more aggressively.
d. knee injuries, neck and back pain, and weakness in the hands develops when poor bike training is used.