—It ________ in Rio do Janciro of Brazil in August，2016．
A：held
B：is held
C：will be held
—Oh, I forgot to tell you. Many children ____ (celebrate) Ann's birthday.
已知等式 1n(n+1)=1n−1n+1 ，对任意正整数n都成立．计算： 11×2+12×3+13×4+⋯+1n(n+1) =____．
