I believe the answer is head-on and port (left). The side lights are usually visible to vessels approaching from the front or the side. The red light usually indicates a vessel's port (left) side while the green light indicates a vessel's starboard (right) side. These lights ensure that there is safety at night as the vessels navigate.
Demonstrative pronoun is the answer.
The piano could only be played with 12 fingers, which is rare because humans normally have ten fingers.
Answer:
mitochondrion / mitochondria coming from the apex.