Group 2 element properties and trends

Steps:

• Recall that in Group 2, atomic radius increases down the group due to more electron shells.
• Reactivity with water and hydroxide solubility also increase down the group.
• Statement A describes a specific use of CaCO3, identifying Q as calcium.
• Without specifying which metal is R relative to Q=Ca, trends cannot uniquely identify the statement for R.

Why B is correct:

• Not enough information to confirm, as B assumes R is below Q, but pair not defined.

Why the others are wrong:

• A is the property assigned to Q (calcium carbonate use).
• C and D require R below Q for truth, but ambiguous without exact identities.
• Overall, question lacks details on Q and R positions.

Final answer: Not enough information.