问题
选择题
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
答案
答案：A
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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
答案：A