I'll never forget （） you for the first time.

单项选择题Experiments in the photography of moving objects （） in both the united states and Europe before 1990.

A．have been conducting
B．were conducting
C．had been conducted
D．are conducted

单项选择题（） have come up with the solutions to the problem.

A．The boy student
B．The boys student
C．The boy students
D．The boys sutdents