In the code below, which of the marked lines is valid syntax? [6pts] #include 4 5 6 7 8 int main() { const int a = 1; const int *pa = &a; a = 2; // invalid or valid // invalid or valid *pa 2; 9 int b = 2; const int *pb = &b; b = 4; *pb= 4; // invalid or valid // invalid or valid 10 11 12 13 14 15 16 17 18 19 20 = C; int c[] = {3, 4}; int *const pc pc = c + 1; *pc = *C + 1; // invalid or valid // invalid or valid return 0; 2 }