Where is the participle in the sentence "believing the spider-man story would fail because readers would find spiders unappealing, Martin Goodman refused to publish it.

The participle in this sentence is believing.

Explanation:

A participle is a word formed from a verb and which functions as an adjective. Examples are going, coming, washing, enjoying, etc. In the sentence above, there is one participle that can be identified and it is, 'believing', derived from the verb, believe.

Believing is a present participle because it satisfies all the conditions that make a word a participle and it is in the present form. In the sentence, it acts as an adjective describing the action word -believe.

"a" because he is appealing to logic as oppose to appealing to the audience's emotions.