ABC

Do you know your ABC? (U.S.: Do you know your ABCs?)

the ABC of finance

For this reason his heart sank when, emerging from his study into the great hall at quarter to eleven, he met Beaver already dressed and prepared to be entertained; it was only a momentary vexation, however, for while he wished him good morning he noticed that his guest had an A.B.C. in his hands and was clearly looking out a train.