Question 1: In C and C languages, struct ST is the name of data type, and NEW is its alias. See the definition of typedef for details. So choose C.

Question 2: In option C, the output will definitely not be 5.000000 because of the different encoding methods of integers and floating-point numbers in memory. Option b is correct, because it is a feature of UNION type.

Question 3: Because of the different coding methods of unsigned number and signed number, for unsigned number 65535, when it is regarded as signed number, there will be ten negative numbers, option D.