What form is the underlined verb in the sentence?

they have ridden that roller coaster three times already.

--ridden is the underlined word

a.
past participle

b.
past

c.
present participle

d.
present

the central idea of the above passage is following;

central idea: cultural study is very important specially archaeology. grimm's stories very well cater to the importance of cultural relevance.

explanation:

the answer is d. she became an english professor at university of georgia.