Draw dot-and-cross diagrams for ethane and ethene. Refer to the previous question part b)(ii) for details on compounds A and ethene.

You're asking for dot-and-cross diagrams for the compounds mentioned in part b)(ii) of the previous question.
From the flow chart, compound A is formed by the hydrogenation of ethene (CH₂=CH₂) in Step II.

$$\text{CH}_2=\text{CH}_2 + \text{H}_2 \xrightarrow{\text{Ni}} \text{CH}_3-\text{CH}_3$$

So, compound A is ethane (CH₃CH₃).

Here are the dot-and-cross diagrams for ethane (Compound A) and ethene (CH₂=CH₂):

a) Ethane (Compound A, CH₃CH₃)
Each carbon atom has 4