增强自我保护意识是健康成长的关键。假如你独自一人在家，突然一位自称是爸爸朋友的陌生人敲门。这时你会[ ]

A．出于礼貌，开门让客人进来坐坐

B．向邻居或周围人大声呼喊

C．告诉对方父母不在，有事下次再来

D．立即拨打“110”报警

He ______ English for 6 years before he went to college. [ ]

A. had learned

B. has learned

C. learned

D. learns