Which of the following is a bidentate ligand?

Which one of the following is a correct statement?

According to Hess's law,the heat of reaction depends upon:

The centre of the circle $r^2-4r(\cos \theta+\sin \theta)-4=0$ in Cartesian coordinates is

The heat evolved in the combustion of methane is given by the following equation:
$CH_{4(g)} + 2O_{2(g)} \to CO_{2(g)} + 2H_2O_{(l)};$
$\Delta H = -890.3 \, kJ$
How many grams of methane would be required to produce $445.15 \, kJ$ of heat of combustion?