Choose the correct answer

47 We can win only if we remain united , so we must support them the moment  they .........................on strike
A will have gome         B will go      C go             D went 
48 I am sorry . I ..................... that fellow's name already 
A forgot               B have forgotten           C have been forgetting          D  forget 
49 Hoang .................... his email four times a week in order not to miss anything important 
A checks     B will check    C is checking     D check 
50 Nowadays , people ........................... social networks with more and more caution
A uses           B are using           C used               D use