Core Formula/Logic: Convert integer part by repeated division by 2, fractional part by repeated multiplication by 2.
Step-by-Step Solution: 1. Integer part: 4 ÷ 2 = 2 remainder 0.
2 ÷ 2 = 1 remainder 0.
1 ÷ 2 = 0 remainder 1.
Read remainders backward: 100.
2. Fractional part: 0.625 × 2 = 1.25 → integer part 1, new fraction 0.25.
0.25 × 2 = 0.5 → integer part 0, new fraction 0.5.
0.5 × 2 = 1.0 → integer part 1, new fraction 0.
Read integer parts forward: 101.
3. Combine: 100.101.
Common Pitfall: Incorrect integer conversion yields 100.001 (option A). Wrong fractional multiplication sequence gives 100.110 (option B) or 100.011 (option D).
Shortcut/Takeaway: Recognize 0.625 = 5/8 = 1/2 + 1/8 = 0.5 + 0.125. In binary, 0.5 is 2^-1 (0.1) and 0.125 is 2^-3 (0.001), so .101 directly.