premise: A BMX rider is in midair while on a dirt trail. hypothesis: The BMX rider is at home watching the X games.
contradiction: The BMX rider is either on a trail or he/she is at home; they cannot be both places at once.|contradiction: If a BMX rider is midair on a dirt trail they can not be at home watching X Games.|contradiction: the bmx rider cant be midair and at home at the same time.