Answer:
B.........................
Well an adjective is describing something like "running" so I guess when you catch a thief, arrest him? hang him? idk
The gerund in the sentence provided above is backpacking. Gerunds are verbs in -ing form but function as a noun. In this sentence, it functions as a direct object because it answers the question "what". By this, we can construct the question "What popular pastime is being talked about?".
I think is b but I am not sure