Are home robots more expensive than doctor ones?

Are home robots more expensive than doctor ones?
A. Are doctor robots more expensive than home ones?
B. Are doctor robots less expensive than home ones?
C. Are home robots as expensive than doctor ones?
D. Are home robots as expensive than doctor ones?
 
Chọn đáp án: B
Giải thích:
cấu trúc so sánh kém “be + less + adj dài + than”
Dịch: Có phải robot giúp việc đắt hơn robot bác sĩ không?