how do you know this is a boulder? none of the above both it a very small rock it a very big rock

how do you know this is a boulder? none of the above both it a very small rock it a very big rock
Answer
Brief Explanations:
A boulder is defined as a very large rock. Small rocks are not boulders. Since the options include the correct characteristic (very big rock) and no other correct - only options are present, the answer is based on this definition.
Answer:
it a very big rock