Lets do process of elimination!
A. Breaking glass - That is a psychical change because if you break it, it is still glass. It didn't change to another substance.
B. Melting ice on a windshield - During the melting process, there is no chemical change, and therefore, no new substance is created.
C. Burning gasoline - When gas burns it usually combines with oxygen to give carbon dioxide, water etc. It is a chemical change.
D. Denting a bumper - The bumper is still a bumper, only thing is it has a dent in it. The properties did not change, meaning no chemical change.
D there is one kind of cell of which all living things are made
7.5 is the answer. You have to move the decimal 2 places to the right.