. . . . . . . . decompose the elements of x into mantissa and twos exponent.

The correct answer is C. frexp.

The frexp function decomposes a floating-point number x into a mantissa and a twos exponent. The mantissa is a floating-point number between 1 and 2, and the twos exponent is an integer between -128 and 127. The frexp function returns a pointer to the mantissa and a pointer to the twos exponent.

The trunc function rounds a floating-point number x down to the nearest integer. The fmod function returns the remainder of x divided by y. The ldexp function multiplies a floating-point number x by a power of 2.

Here is an example of how to use the frexp function:

```

include

include

int main() { double x = 3.14159; double mantissa, exponent; frexp(x, &mantissa, &exponent); printf("The mantissa is %lf\n", mantissa); printf("The exponent is %d\n", exponent); return 0; } ```

This program will print the following output:

The mantissa is 3.14159265358979323846 The exponent is 1