Provide your best answer for the following question. Give ONLY the answer, no other words or explanation.
For example:

Answer: <most likely answer, as short as possible; not a complete sentence, just the answer!>.

The question is: A student stands outside on a cold winter day. His hands become cold and he rubs them together to make them warmer. Which statement explains why rubbing his hands together makes them warmer?
Rubbing increases blood flow to the hands, allowing them to absorb more body heat.