Asubstance composed of two or more elements in a fixed, definite proportion is
a. a homogeneous mixture.
b. a heterogeneous mixture.
c. a compound.
d. a solution.
e. an alloy.

under a microscope, cancer cells may look very different from normal cells. they often have different sizes and some may be larger than normal while others are smaller. cancer cells are often abnormally shaped and the control centre of the cell (the nucleus) may have an abnormal appearance.

i think? ?

i think it's letter a.