This speech is persuasive because it a. attempts to explains vegetarianism to audience b. attempts to defines vegetarianism to audience c. attempts to convince audience to become vegetarian d. attempts to demonstrate vegetarianism to audience

Ther correct answer is: C) attemps to convince the audience to become vegetarian.

In a persuasive speech, the author tries to persuade an audience to accept an idea, attitude , or action. To do this, argumentation, rationalism, symbolism, and the usage of supportive information is needed.

In this case we can figure out that the speech is persuasive because the author is trying to modify the behaviour of the audience. he wants them to stop eating meat.  The word "convince" gives us an important clue as it means "persuade (someone) to do something".

The other options only gives information on vegetarianism without seeking to provoque an action on the audience.