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.
The red sidelight is called so because this light is visible to another boat that is moving towards the powerboat either from the side or in the head on the direction.
Besides the red light, another side light that is present in the green light.
Both fo the side lights are visible to the boats coming from the head-on direction. Besides this, the red light is visible to the boat coming from the left side which is called the port side.
Between one-third and one-half of all fertilized eggs never fully implant. A pregnancy is considered to be established only after implantation is complete
