How ______ it is to see the big playground covered by the white snow.
A:delightful
B:grateful
C:careful
D:colourful
_______ Su San?
C 10 =40;
C 30 +C 31 =41;
C 50 +C 51 +C 52 =42;
C 70 +C 71 +C 72 +C 73 =43;
…
照此规律,当n∈N*时,
C 2n−10 +C 2n−11 +C 2n−12 +…+C 2n−1n−1 =____.
It was such a funny show that people couldn't help again and again.
中国“北京人”处于世界人类进化过程中的( )
激光是一种人造光,其主要特点有那些?