True meridians are generally preferred to magnetic meridians because

ANS:C - these remain constant.

True meridian: Geographic North pole and the south pole is the called the earth true meridian.

Magnetic meridian: The magnetic north pole and south pole direction is called Magnetic meridian.

THE MAGNETIC MERIDIAN CHANGES WITH TIME, so it not good to preferred in fieldwork.

The true meridian (geographic north-south pole direction) remains constant always.

So, the answer is "C".