Answer: To enable the use of the rand function in C++, you need to include the <cstdlib> header file. This header file contains the declaration of the rand function, as well as other functions and constants related to random number generation.
Here's the preprocessor directive you can use to include the <cstdlib> header file:
cpp
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#include <cstdlib>
Once you've included this header file, you can use the rand function to generate random numbers in your program. Remember that you'll also need to call srand to seed the random number generator before using rand.
Step-by-step explanation: