The world in bold is a past participle. Option A is correct.
A participle is a word formed from a verb, usually by adding -d, -ed, or -ing. A participle is a form of a verb that can be used in compound tenses of the verb
There are two kinds of participle:
The present participle which ends with -ing and the past participle which ends with -d or -ed for regular and with -t or -en or some other form for irregular.
