（5分）（2011•重庆）从甲、乙等10位同学中任选3位去参加某项活动，则所选3
题型：填空题
问题：
（5分）（2011•重庆）从甲、乙等10位同学中任选3位去参加某项活动，则所选3位中有甲但没有乙的概率为 ．
题型：填空题
阅读短文，判断正误（正确的写T，错误的写F）。
Imagine the year is 1666 and we can see a student called Isaac Newton. He's away from his university
for a holiday and at home with his family. Isaac Newton continues to study at home. He enjoys physics and
thinking about the mysteries of the world.
On a day when there is rain and sun at the same time he sees a beautiful rainbow in the sky. It has many
different colours, he is told that there are five. Newton wants to have his own rainbow because he wants to
look at it closely. He decides to do an experiment. On a sunny day he goes inside a small room and he makes
the room very dark. Then he makes a small hole and the sun comes inside, it's a small ray of light. It's white.
Newton takes a prism (棱镜) and holds it up to the light. The ray of light goes through the prism, but it isn't
white now there are many colours. The prism has split up (分解) the white light into different colours: Newton
has a rainbow.
Newton looks at his rainbow carefully. He can see more than five colours, he can see seven. He says the
colours are: red, orange, yellow, green, blue, indigo and violet.
But Newton is a scientist and he's always very interested in how things work. He has his rainbow but he
wants to know more. So he takes another prism and holds it up to the rainbow. The rainbow goes through the
second prism, but it isn't colourful now-it's white again. The prism has joined up the colours back into white
light. Newton is the first person to understand that light is a combination of all the rainbow colours together.
Newton also understands how we can see colour. Imagine a leaf in the sunshine. All the rainbow colours
fall on the leaf but it absorbs (吸收) all these colours. The only colour that is reflected (反射) is green, so the
leaf looks green. Different objects reflect different colours. And perhaps Newton's favourite fruit is an
orange-but what came first, the name of the fruit or the name of the colour?
( )1. In 1666 Isaac Newton was a university student learningphysics.
( )2. Newton was told that there were five colours in a rainbow and he believed it.
( )3. Newton used a prism to split up the white light from the sun.
( )4. Newton understood that light was a combination (复合) of all the rainbow colours together.
( )5. Different objects reflect the same colours.