He likes playing tricks on others, but _________, he is a good boy. He is willing to help others.
A：in this way
B：in some ways
C：in his way
D：on his way
理发时，为了避免发屑沾到衣服上，经常在人身上围上一块布，理完发后，理发师用力抖动布将发屑去掉．请问理发师抖掉发屑的做法，属于哪种物理现象，并加以解释．
