21.Many types of rock are ____ from volcanoes as solid,fragmentary material.

　　A) flung

　　B) propelled

　　C) ejected

　　D) injected

　　22. With prices ____ so much,it is difficult for the school to plan a budget.

　　A) vibration

　　B) fluctuating

　　C) fluttering

　　D) swinging

　　23.The person who ____ this type of approach for doing research deserves our praise.

　　A) originated

　　B) speculated

　　C) generated

　　D) manufactured

　　24.____ that the demand for power continues to rise at the current rate,it will not be long before traditional sources become inadequate.

　　A) Concerning

　　B) Ascertaining

　　C) Assuming

　　D) Regarding

　　25.Her jewelry ____ under the spotlights and she became the dominant figure at the ball.

　　A) glared

　　B) glittered

　　C) blazed

　　D) dazzled

　　26.Connie was told that if she worked too hard,her health would ____.

　　A) deteriorate

　　B) degrade

　　C) descend

　　D) decay

　　27.We find that some birds ____ twice a year between hot and cold countries.

　　A) transfer

　　B) commute

　　C) migrate

　　D) emigrate

　　28.As visiting scholars,they willingly ____ to the customs of the country they live in.

　　A) submit

　　B) conform

　　C) subject

　　D) commit

　　29.More than 85 percent of French Canada's population speaks French as a mother tongue and ____ to the Roman Catholic faith.

　　A) caters

　　B) adheres

　　C) ascribes

　　D) subscribes

　　30.The professor found himself constantly ____ the question:"How could anyone do these things?"

　　A) presiding

　　B) poring

　　C) pondering

　　D) presuming