Two effector neurons for muscle fibres were stimulated electrically and their responses were noted.

In an experiment, two effector neurons for muscle fibres were stimulated electrically and their responses were noted. The effector neuron for muscle fibre 1 had a threshold level of 18 mV. The effector neuron muscle fibre 2 had a threshold level of 32 mV.

In a separate investigation, a student used an electrical probe to stimulate these same two effector neurons for the muscle fibres. The student began with a voltage of 5 mV. For each sequential test, the voltage was increased by 10 mV.
 
Row
Stimulus Voltage
Response of Muscle Fibre 1
Response of Muscle Fibre 2
A
15 mV
relaxed
contracted
B
25 mV
contracted
relaxed
C
35 mV
contracted
relaxed
D
45 mV
relaxed
relaxed

Which row identifies correctly the status for each muscle fibre during stimulation?
Select one:
a. C
b. A
c. D
d. B