Chemistry question ionisation energy

Hi, please could i have help on this question? I thought the answer would be c because the lowest ionisation energy will mean that it will give its outer electron easily but the answer is A?

Here is the question: https://app.gemoo.com/share/image-annotation/584502434083774464?codeId=v6ggx1mrElk19&origin=imageurlgenerator
Thanks!

They tell you compound XH is covalent. This allows you to make some useful deductions:

-It’s most likely a non-metal, since the bonding is covalent - had it been an ionic compound, you would have been correct to choose C.

-It’s most likely a halogen, since it only forms one bond in the compound XH.

Now you just have to try using the ionisation energy trends to identify which of the four elements on the graph is most probably a halogen.

Ohh so would it be A because it is in group 7 and B would be a group 8 with the highest ionisation energy since it is stable and it would be harder to lose an electron?

That is exactly it.

They’ve shown the last two ionisation energies on one period and the first two ionisation energies on the next in the graph, which I thought was rather mean.