Answer:
3) You will enjoy the manu activities, such as horseback riding, hiking, or camping.
Step-by-step explanation:
Gerund can be defined as a verb form that acts as a noun and is most notable for its -ing ending.
However, every option here contains an -ing form.
But options 1) and 4) use -ing forms as a verb used to make Present Continous Tense.
Option 2) contains -ing form, but in a form of adjective, it explains what are art and nusic festivals like.
Finally, option 3) uses gerund, since -ing form functions as a noun (riding, hiking, camping).