In this task, you're given a pair of sentences, sentence 1 and sentence 2, that agree with each other. Your job is to alter sentence 2 so that the pair contradict each other. Generated sentences must be short, with less than 15 words. New information can be introduced. Avoid using pronouns to confuse the subject of the sentence.

Sentence 1: Two children, one wearing purple, the other black, ride a single bike on the pavement. Sentence 2: Two children ride the same bike.
Two adults ride a double seater bike.

Sentence 1: A young man in a blue shirt and white shorts sitting with his guitar. Sentence 2: A man sits with his guitar.
A man sits with his pet unicorn in the grass.

Sentence 1: A young boy does skateboarding tricks down metal stairs. Sentence 2: A kid is skateboarding and doing tricks.

A kid is doing tricks on his bicycle.