A boss can do a job in two days if his four secretaries A, B, C and D are all present. Their efficiency got reduced to 1/6,1/4,1/3 and 1/2 respectively according as A, B, C and D remains absent. In any day only one secretary remains absent. Also the boss finishes his work exactly in integral number of days. Which of the following secretaries cannot be absent for an odd number of days?