問題詳情
45-50 題組 Hummingbirds live only in the Americas, __45 most of their time in the warmer climates. They seem to be able to __46 the changes in the length of days as well as the changes in the insect and flower —47—• Before winter comes, they move south to —48— the cold and find enough food. In spring they start —49— back to ther birthplace to breed. Researchers believe that some hummingbirds fly non-stop over the Gulf of Mexico, —50— covering 500 miles in more than 18 hours!
【題組】45
【題組】45