Which sentence demonstrates correct subject-verb agreement?

ADave Wiens, a Denver native and champion mountain biker, helped design the Olympic mountain bike course in Atlanta, Georgia.
BExploring international mountain passes, such as those in New Zealand, Canada, and Japan, are one of the biker’s favorite hobbies.
CWiens’s competitors, such as John Tomac and Mike Kloser, inspires him to train more aggressively.
DKnee injuries, neck and back pain, and weakness in the hands develops when poor bike training is used.

Verified Answer :

let's look at the sentences without the relative clauses, this should make it easier:a. Dave Wiens helped design the Olympic mountain bike course in Atlanta, Georgia.

BExploring international mountain passes are one of the biker’s favorite hobbies.
CWiens’s competitors inspires him to train more aggressively.
DKnee injuries, neck and back pain, and weakness in the hands develops when poor bike training is used. We see here that in the first sentence "Dave Wiens helped" - and this is correct. Option A is correct. In C it should be "competitors insipire" and in B exploring...is". in D we have a number of things, so it should be "develop"

the correct answer is : Dave Wiens, a Denver native and champion mountain biker, helped design the Olympic mountain bike course in Atlanta, Georgia.