Which two signs and two numbers should be interchanged to make the given equation correct?27 + 66 – 7 ÷ 21 × 4 = 81

• A. 27 and 7, + and ÷
• B. 4 and 7, ÷ and ×
• C. 66 and 21, + and –
• D. 4 and 7, + and ×