constant effort. Concentration means that you must accept only about the work at hand. since part of the mind is waiting for a telephone call or listening to the radio or television, that rest of the mind cannot ponder study.
Some subjects ... us naturally, and we enjoy studying them. Others may require a real effort of the will. but no subject needs be dull if it is approached with a .... to master it. A subject sometimes only seems dull .... we do not understand the reasons for studying it. After its purpose is ....., it may become interesting.