Tomlookssopaletoday．He____ill.（） A: mustbe B: hadtobe C: shouldbe D: shallbe

Thelightison.He___________________athome.（） A: musthavebeen B: wouldbe C: mustbe D: willbe

Bythetimeof1969,thereweremanyspaceexplorations. A: havebeen B: mustbe C: hadbeen D: musthavebeen

A lifeboat is weight tested by lowering to near the waterand loading to capacity with weight evenly distributed. Itis then lowered into the water and released. This test mustbe done at least once every（）.