Static stretches are part of an effective cool down because they can

a) improve performance
b) decrease blood flow
c) prevent overload
d) increase range of motion

Static stretches are part of an effective cool down because they can help to decrease blood flow after a work out, so the answer to this question is B. Decreasing blood flow after a work out is important to avoid dangerous outcomes such as blood pooling. I hope this answered the question for you.