Step 1: Note where the atoms sit.
A BCC cell has atoms at \( (0,0,0) \) and \( (\frac{1}{2},\frac{1}{2},\frac{1}{2}) \), and whether a plane \( (hkl) \) reflects X-rays depends on whether the waves scattered by these two atoms reinforce or cancel each other.
Step 2: Compare the phase from each atom.
The second atom is offset by half a cell in each direction, which brings in a phase factor of \( e^{i\pi(h+k+l)} \) relative to the first atom.
Step 3: Check when the waves add or cancel.
If \( h+k+l \) is even, this factor equals \( +1 \), so the two atoms scatter in phase and reinforce, giving a visible reflection. If \( h+k+l \) is odd, the factor equals \( -1 \), so the waves cancel exactly, and no reflection appears. This is why planes like (100) and (111), with odd index sums, are missing from a BCC pattern while (110) and (200) show up strongly.
So reflections in a BCC lattice only survive when \( h+k+l \) is even, option (B).