Answer: The correct answer is Option c.
Step-by-step explanation:
It is given that the valence electrons of the substance's atoms feel an effective nuclear charge of +1 and its radii is larger than the Potassium atoms.
The elements which belong to group 1 shows an effective nuclear charge of +1. Therefore, the given substance also belongs to group 1.
In a group, the ionization energy decreases as we move down the group as the size increases and thus the valence shell moves farther from nucleus and thus is easier to remove.
Electronegativity also decreases as we move down the group as the size increases, thus the affinity for incoming electron decreases.
Hence, the correct answer is Option c.