Explanation:

To determine which two signs should be interchanged to make the equation "4 + 5 - 16 × 4 ÷ 2 = 1" correct, let's explore each option:

- Option 1: Swap + and -: Replacing these signs, the equation becomes 4 - 5 + 16 × 4 ÷ 2, which upon simplifying, doesn't yield 1.

- Option 2: Swap ÷ and ×: This changes the equation to 4 + 5 - 16 ÷ 4 × 2. Simplifying, the equation becomes 4 + 5 - 4 × 2 = 1, which is correct.

- Option 3: Swap ÷ and -: This gives 4 + 5 ÷ 16 × 4 - 2, which simplifies to a result different from 1.

- Option 4: Swap + and ×: The equation is now 4 × 5 - 16 + 4 ÷ 2, which doesn't simplify to 1.