——Last month I traveled across the Sahara Desert by ______ camel with some locals. ——What ________ amazing experience!
A：the;an
B：a;/
C：/;the
D：/;an
在晴天中午，密闭的玻璃温室中栽培的玉米，即使温度及水分条件适宜，光合速率仍然较低，其主要原因是
