Hydrogen boils at 20k. what is the boiling point of hydrogen on the celsius scale

Celsius scale is related to kelvin scale by the following equation,

⁰C = K-273

°C = K-273  

So as here temperature is given in kelvin, so it can be converted into celsius as follows:

So 20 K = 20K-273 °C  

= -253 °C .

So, the 20 K temperature equals to -253 °C.

So , -253 °C is equals to  20 K or 20 K temperature equals to -253 °C.

b..

is the correct one

explanation:

covalent bonds form as valence electrons are shared between two atoms. lewis structures and structural formulas are common ways of showing the covalent bonding in organic molecules. formal charge describes the changes in the number of valence electrons as an atom becomes bonded into a molecule.