We must keep the noise under 50dB(分贝) here.The noise must ______ ______under50dB here

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Wemustkeepthenoiseunder50dB(分贝)here.Thenoisemust____________under50dBhereWemustkeepthenoiseunder50dB

We must keep the noise under 50dB(分贝) here.The noise must ______ ______under50dB here
We must keep the noise under 50dB(分贝) here.The noise must ______ ______under50dB here

We must keep the noise under 50dB(分贝) here.The noise must ______ ______under50dB here
be kept
be controlled
变为被动语态吗?