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(1) Removing water vapor requires a water-absorbing substance, which can only absorb water and cannot react with carbon dioxide, so concentrated sulfuric acid is used to remove water.

So the answer is: concentrated sulfuric acid;

(2) When collecting gas with this device, if the gas with density greater than air is collected by exhaust method, it will enter from the "long" end; The gas whose density is less than air enters from the "short" end. Hydrogen is less dense than air, so it enters from the B end.

So the answer is: B.