Its going to he b.grasses because most animals eat grass
In order to answer this, we mus know the data for the heat of combustion of propane. This is an empirical data that you can search online. The heat of combustion is -2220 kJ/mol. The molar mass of propane of 44.1 g/mol. The solution is as follows:
ΔH = -2220 kJ/mol (1 mol/44.1 g)(1000g/1kg)(20 kg)
<em>ΔH = -1006802.721 kJ or -1 GJ</em>
Ten protons would be Neon, but the most stable? I'd have to say 12 neutrons in contrast to the 10 protons. Not too negative in balance.