Which sentence has an infinitive phrase that functions as a subject a. plants are adapted to take in moisture from the ground b. to convert sunlight and energy into food is the end result of photosynthesis c. after the rain water travels from the ground to the roots of a plant

What is implied in this sentence from mark twain's "the £1,000,000 bank-note"? i was puzzled, and wanted to discuss the matter a little further, but they didn't; so i took my leave, feeling hurt and insulted to be made the butt of what was apparently some kind of a practical joke, and yet obliged to put up with it, not being in circumstances to resent affronts from rich and strong folk.