Assertion (A): Variables declared inside a function are local to that function by default.

Reasoning (R): A function can access global variables if they are explicitly declared with the global keyword inside the function.

Both A and R are true, and R is the correct explanation of A.

Explanation — By default, variables declared inside a function are local to that function, meaning their scope is limited to the function itself. However, a function can access and modify global variables only if they are explicitly declared with the global keyword inside the function. Otherwise, the function will treat the variable as local.