Final answer:
The correct answer is c. long float. In C, long float is not a valid type, while unsigned long, short unsigned int, and long double are valid types.
Step-by-step explanation:
The correct answer is c. long float. In the C programming language, long float is not a valid type. The available standard data types in C include unsigned long, short unsigned int, and long double. The unsigned long type represents positive integers, the short unsigned int type represents positive integers up to a certain maximum value, and the long double type represents floating-point numbers with extended precision.
Learn more about C programming language