21. For Americans ______ things are a little easier, thanks to _______ work of Noah Webster, ______ teacher who graduated from Yale University in 1778.
A. the; the; a B. 不填; the, a C. the; 不填; the D. 不填；不填; one
22. The moment a ship came in sight, the captain immediately gave an order to send out a rescue ______.
A. sign B. sight C. symbol D. signal
