Which sentence contains a restrictive clause?

Question

The road, which was long and winding, took us deeper and deeper into the dark forest.
The parrot, which must have been tame, flew out of the tree and landed on my shoulder.
Aware that I could be bitten, I carefully approached the trapped dog, which growled at me.
The astronaut who first stepped on the moon was Neil Armstrong.

Answer 1

The sentence that contains a restrictive clause is:

The astronaut who first stepped on the moon was Neil Armstrong.

In this sentence, "who first stepped on the moon" is a restrictive clause because it provides essential information to identify which astronaut is being referred to.