the safety of gas, the government has ch
题型:选择题
问题:
the safety of gas, the government has checked the city's gas supply system thoroughly.[ ]
A. To ensure
B. Ensuring
C. Having ensured
D. To have ensured
the safety of gas, the government has checked the city's gas supply system thoroughly.[ ]
A. To ensure
B. Ensuring
C. Having ensured
D. To have ensured