5.
On a recent trip to California,I stopped by Natural Bridges,where the monarch butterflies overwinter.Many years ago,I livedclose enough to it that I could walk there regularly and study their gatherings-the most memorable experiences when living in California,This visit,however,turned out to be disappointing.Though the way to the protected monarch garden looked just as I remembered it,I spotted only a few butterflies there.So I had to drive about a mile south to Lighthouse Field a more open area visited by large numbers of bikers,dog walkers and tourists.Many monarehs-at least several hundred-gathered in a small forest of pines there.Why had they moved to this less hospitable habitat-John Dayton,a biologist from San Jose provided an answer.During the 1990s,a deadly disease killed off most large pines sheltering the monarch habitats at Natural Bridges,forcing monarchs to seek shelter elsewhere.Still,since the mid-1990s,the number of overwintering monarchs in California has declined by nearly 90 percent.Butterfly populations at Santa Paula alone,for example,have dropped from about 120,000 to less than 1,000-the lowest figure in two decades.
In California,coastal development has reduced the area suitable for overwintering monarchs. Illegal logging,poorly regulated tourism and water withdrawals near the butterfly habitais are also endangering the butterflies.
Throughout the butterflies'North American range,declines in milkweed plants-which monarchs need to reproduce-are also knocking down the insect's numbers.Chemicals are widely applied,wiping out the milkweed once growing in the agricultural land.
Climate change may worsen the monarchs'situation.As atmospheric levels of CO
2 continue to rise,milkweeds are likely to produce fewer toxic compounds(有毒化合物) that protect both butterflies and caterpillars (幼蟲) from their enemies.Milkweed leaves also may get tougher. Caterpillars will have a harder time chewing the leaves.
66.Why did the author feel disappointed during his revisit to Natural Bridges?C
A.Because it had been overpopulated with Monarchs.
B.Because the monarch's living habit was changed a lot.
C.Because fewer monarch butterflies overwintered there.
D.Because the people there were not so hospitable as before.
67.Where did the author find those monarchs moved?A
A.Natural Bridges B.Lighthouse Field
C.San Jose D.Santa Paula
68.What caused a sharp decline of overwintering monarchs according to Para 3?A
A.The loss of large pines. B.A disease of monarchs.
C.Water pollution. D.Too many caterpillars.
69.According to the passage,the decline of the milkweeds is connected withD.
A.coastal development B.illegal logging
C.poorly regulated tourism D.the abuse of chemicals
70.Which diagram shows correctly how the passage is developed?(P=paragraph)D