Which of the following describes a properly controlled experiment

Aneuron is stimulated with an electric pulse. the action potential is detected at a point 3.70 cm down the axon 0.0052 s later. when the action potential is detected 7.20 cm from the point of stimulation, the time required is 0.0063 s. what is the speed of the electric pulse along the axon? (why are two measurements needed instead of only one? )

Which statement correctly describes a way that mutations increase the likelihood that a species will survive in a changing environment

Ais a group of individuals of the same that exist together in the same place at the same time