请选择ABC:`*o,n2{'^7Y7f*SThe students couldn't help ______ when they heard the joke.9p.I2c+w*N0^6@/j;x-B0D3q
A.to laugh9p.I2c+w*N0^6@/j;x-B0D3q
B. laugh9p.I2c+w*N0^6@/j;x-B0D3q
C. laughing9p.I2c+w*N0^6@/j;x-B0D3q