Extract number in bits from b1 to b4 of each byte

We want to change each byte of an int to the number in bits from b1 to b4 of that byte. The bits of a byte are numbered from 0 to 7 as b7..b0. As an example take this int in C++:

int x = 0x1A390B45;
// Decimal 439946053
// Binary 00011010 00111001 00001011 01000101

This is a (partial) C++ solution we have:

unsigned char* p=(unsigned char*)&x;
for(int i=0; i < sizeof(int); i++) {
    /* ?? */
}

We have omitted one line of code above for you to fill in. Which one of following choices should replace the comment (/* ?? */) in above code?