Assuming get$\_$size is a constexpr function that takes no arguments and returns an int value, which of the following array definitions are illegal?

A constexpr function is one that is evaluated at compile time, allowing its use in situations where a compile$-$time constant is required, such as for array sizes. This is essential here because standard $C++$ requires that array sizes be known at compile time to allocate the appropriate amount of memory.

none of these

float ia$[$get$\_$size$()]$;

void ia$[$get$\_$size$()]$;

double ia$[$get$\_$size$()]$;

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