B. is doing
C. are doing
D. did
Giải bởi Vietjack
Đáp án đúng: C
Giải thích: Cấu trúc thì hiện tại tiếp diễn: S + is/are/am + V-ing
Dịch: Chúng tôi đang thực hiện một bài tập về thì hiện tại tiếp diễn vào lúc này.
Fill in each numbered blank with one suitable word or phrase
Post Office service is (1) _______ developing with some certain inventions. The first envelopes were made (2) _________ cloth, animal skins, or vegetable parts. The Babylonians wrapped their messages in thin sheets of clay that were then baked. In 1653, a Frenchman, De Valayer established a postal system in Paris. He set up mail boxes and delivered any letters placed in them if they used envelopes which only he sold. (3) ______ enemy put live mice into the letter boxes and ruined De Valayer's business.
A schoolmaster from England, Rowland Hill (4) ________ the adhesive postage stamp in 1837, an act for (5) _______ he was knighted. Through his efforts the first stamp in the world was issued in England in 1840. Hill created the first uniform postage rates that were based on weight, rather than size.
Scientists around the world have been studying the warming of waters in the Pacific Ocean known as EL Nino. The appearance of EL Nino is known to affect the weather around the world. Scientists still do not completely understand it. Yet they now find they can use it to tell about the future in different areas of the world.
One example is the work of two scientists at Columbia University in New York, Mark Cane and Gordon Eshel. A scientist of Zimbabwe, Roger Buckland worked with them. They have found that when EL Nino appears, Zimbabwe has little or no rain. This means corn crops in Zimbabwe are poor. The last EL Nino was in 1991 to 1993. That was when southeastern suffered a serious lack of rain.
The scientists wrote about their recent work in the publication "Nature". Their computer program can tell when an EL Nino will develop up to a year before it does. They suggest that this could provide an effective early warning system for southern Africa, and could prevent many people from starving.
EL Nino is known as ......................
Visitors with more abundant travel budgets can enjoy the comfort of five-star hotels and luxury cruise ships.
Mark the letter A, B, C, or D to indicate the word(s) OPPOSITE in meaning to the underlined word(s) in each of the following questions
Tourists can do and see a lot in Ha Long Bay at a reasonable price.
Find the mistake: It is very difficult for her to prevent him for smoking in her house.
If the wind does not blow, there is no...............wind energy.
