To round is to delete or (66) one or more of the least significant digits in a positional (67) and to, or not to, adjust the part retained in accordance with some specified rule. The purpose of rounding is usually to limit the (68) of the numeral or to reduce the number of characters in the numeral, or to do both these things.

The most common arithmetic forms of rounding are rounding down, rounding up and rounding off. Rounding down is defined as making no adjustment to the part of the numeral that is retained. Rounding up means adjusting the part of the numeral that is retained by adding 1 to the least significant of its digits and executing any necessary carries, if and only if One or more non-zero digits have been deleted. Rounding off (69) adjusting the part of the numeral retained by adding 1 to the least significant of its digits and executing any necessary carries, if and only if the most significant of the digits deleted was equal to or greater than half the (70) of its digit place.

（69）处填（）。

A．specifies

B．regulates

C．refers to

D．assigns

阅读下列文字，回答后面的问题。

       罗贯中在《三国演义》里，写到晋国的司马炎灭了吴国，俘虏了吴王孙皓。在接见孙皓时，司马炎说了一句：“朕设此座已久矣。” 司马炎这句话的言外之意是什么？