a.
using a wide range of temperatures during an experiment
b.
studying animals in different habitats and under different circumstances
c.
keeping a chemical’s concentration the same in all parts of an experiment
d.
studying fixed objects such as the stars
using a wide range of temperatures during an experiment
b.
studying animals in different habitats and under different circumstances
c.
keeping a chemical’s concentration the same in all parts of an experiment
d.
studying fixed objects such as the stars
-
(c).