Final answer:
The conditional statement in the sentence is 'I won't be able to ride bikes.'
Step-by-step explanation:
The conditional statement in the given sentence is B. I won't be able to ride bikes.
The word unless in the sentence indicates a conditional relationship between the two parts. The first part states that the student's headache needs to go away, and the second part states the consequence, which is that the student won't be able to ride bikes.
Conditional statements are commonly used to express cause and effect relationships, and they are an important part of understanding logical reasoning in English and other subjects.