将阻值为40 Ω的电阻丝接在电源两端，通电10 min，电流产生的热量是1.5×10³ J，若将阻值为10 Ω的电阻丝接入同一电源的两端，通电10 min，电流产生的热量是[ ]

A. 1.5×10³ J    

B. 3.75×10³ J    

C. 7.5×10³ J    

D. 6.0×10³ J    

The old man became very worried, standing at the gate, unable to find a man________he could turn for

help. [ ]

A. from whom  

B. at whom

C. into whom  

D. to whom