卵巢内类固醇激素合成的途径为

A．胆固醇→孕激素→雄激素→雌激素

B．胆固醇→孕激素→雌激素→雄激素

C．胆固醇→雄激素→雌激素→孕激素

D．胆固醇→雌激素→雄激素→孕激素

E．胆固醇→雄激素→孕激素→雌激素

With the country’s population increasing to 1.3 billion, many of China’s rivers, including the legendary Yellow River,       .

A．is drying up

B．will be drying up

C．had dried up

D．are drying up