How does the speaker feel about the regulation of mobile services in India

A．It has produced desired effects.

B．It has more advantages than disadvantages.

C．It helps promote competition.

D．It has created a negative impact in the market.

不同地层时，对于粘性土盾构标准掘进速度应为（）mm/min。

A、25~30

B、20~25

C、10~20

D、30~4000m