—Every four years. My father and I will go to Russia to enjoy the exciting games this summer.
A:how long the World Cup is held
B:when you will go to Russia
C:who you will go to Russia with
D:how often the World Cup is held
In the word“matches”,the underlined part is pronounced(发音)_______.
已知双曲线 x2a2−y2b2 =1(a>0,b>0)的一条渐近线为2x+y=0,一个焦点为( 5 ,0),则a=____,b=____.