Final answer:
When accelerating on an easterly heading, a compass would still point towards the Earth's magnetic north. The compass needle aligns with the Earth's magnetic field which leads to the magnetic north, typically shown as 'north' on a compass.
Step-by-step explanation:
If you were to accelerate on an easterly heading, your compass would still show the direction of the Earth's magnetic north, which in general terms is 'north'. The compass needle aligns itself with the Earth's magnetic field, which points towards the magnetic north pole. Therefore, the correct answer is (a) North. It is important to understand that the needle of a compass is a magnet, and the north pole of the compass needle is attracted to the magnetic south pole of the Earth, which is approximately aligned with the geographic north pole. Hence, no matter if you are accelerating, moving at a constant speed, or even at rest, if your compass is working properly and there are no other strong magnetic fields around that could interfere with it, it should point north.
Another interesting aspect to understand is the concept magnetic declination, which is the difference between the magnetic north and the geographic north. Depending on where you are on Earth, this declination must be accounted for when navigating with a compass. However, for the purpose of this question which assumes we are ignoring external factors, this concept does not change the answer.