At the first sight the planet Mars does not appear very welcome to any kind of life. It has very little oxygen and water, the temperature at night is below -50~Cand winds of 100 miles per hour cause severe dust storms. However, the surface of the planet seems to show that water flowed across it some time in the past, and it is believed that there is enough ice at the poles to cover the planet with water if it melts. Although there is no life on the Mars now, some scientists think that there may have been some form of life long time ago. At that time, the planet had active volcanoes; the atmosphere was thicker and warmer; and there was water. In fact, in some ways the Mars may have been similar to the Earth, where life exists.
Some people believe that the Mars could support life in the future if the right conditions were produced. The first step would be to warm the planet using certain gases which trap the Sun’s heat in the planet’s atmosphere. With warmth, wa
A. there is no life there now
B. there is a large amount of water at the poles
C. the Mars may be able to support life in the future
D. conditions may have been similar to those on the Earth
One of the first things a visitor does upon arrival in another country is to get to know the local money. American money is unlike the money used in many other countries, since the bills, or paper money, are all the same color and size no matter how much it is. Visitors should be careful to look at the bill before giving it out. Besides, new bills often stick together.
The coins of every country are difficult to learn at first. American coins are represented by the cent sign. Also the size of American coins do not show the value. For example, the 10-cent coin is much smaller than the 5-cent coin, although it is worth twice as much. All United States coins are silver colored, except for the" penny" (one-cent piece), which is a brown coin. Here are more details about American coins.
我来回答:
