Which of the following is a branch of chemistry? biology microbiology all of the above none of the above biophysics

There are five main branches of chemistry including, physical, analytical, biochemistry, organic and inorganic chemistry. I would have to say that the answer to this question is none of the above. The answers given to this multiple choice question are some of the branches of biology. If the question asked for the branches of biology then the answer would be all of the above.

Aquantity of that isotope to decay to 1/2 of  its original value