The way to get the result of floating-point operation is that at least one of the two numbers involved in the operation is a floating-point number.

A. 1.0 defaults to double, so you will get a double result of 0.5.

B. 1 and a are both integer types. In practice, integer operation is installed and the result of integer operation is retained. Then the data type of this integer result will be forcibly converted to float type according to the statement, and 0 will be obtained.

C.A. participates in division after forcibly converting data types, and can get a floating-point result of 0.5.

D. After denominator a* 1.0, the default double-precision result is obtained, and then the double-precision result is obtained by division.