The amino acid with a side-chain pK_a just below neutrality and which plays an important role as a proton donor and acceptor in many enzyme catalyzed reactions is:

the answer would be knowledge about cars!

the main thing i would use is bricks because if there is a hurricane, there is a great possibility for the house to still stand. and i would also use plexiglass windows instead of regular windows because plexiglass isn't prone to breaking.

i think that it is c, d, and e, hope this