1. Assuming the underlined word is 'discarded,' the correct answer is verb. Participles are used in three ways: as an adjective, as an adverb, or as a part of a complex tense (such as present continuous). Given that past simple (used in this sentence) is a simple tense, it is a verb rather than a participle.
2. Assuming the underlined word is 'camping,' the correct answer is participle. Based on my explanation above, you can understand why it is a participle rather than a verb. So, it is used in a complex tense (past perfect continuous + it ends in -ing) which means that it cannot be a verb. If the entire phrase was underlined (had been camping), that would be a verb.
3. Assuming the underlined word is 'cooking,' the correct answer is participle. Although participles and gerunds look the same (both end in -ing), there is a difference between them. Gerunds are only used as nouns, whereas participles are used as either adjectives or adverbs. Here, the word 'cooking' is an adjective, which means it is a participle rather than a gerund.
