下列符号中，只具有微观意义的是[     ]

A．Cu          

B．Cl₂      

C．2H₂          

D．NH₃

Had the US Airways captain not guided his jet to a safe landing on the Hudson River, just west of New York, over 100 people aboard ______, along with many more on the ground.

A．might have died

B．needn’t have died

C．must die

D．shouldn’t die