Step 1: Properties of Group 1
Alkali metals are the most electropositive elements in their respective periods.
Step 2: Analysis
They have the largest atomic radii and effectively shield their valence electrons.
Step 3: Ionization Energy
Because they lose their valence electron easily, they possess the minimum (low) ionization energy in their period, not high.
Step 4: Verification
Options (b), (c), and (d) are true characteristics of alkali metals.
Final Answer: (a)