The correct answer is option D
Cyclopropane is a cycloalkane molecule with the molecular formula C₃H₆, consisting of three carbon atoms linked to each other to form a ring, with each carbon atom bearing two hydrogen atoms resulting in D₃H molecular symmetry. The small size of the ring creates substantial ring strain in the structure.

The correct answer is Option B.

The C-C-C bond angles in cyclopropane (60^o) and cyclobutane (90^o) are much different than the ideal bond angle of 109.5^o.This bond angle causes cyclopropane and cyclobutane to have a high ring strain. However, molecules, such as cyclohexane and cyclopentane, would have a much lower ring strain because the bond angle between the carbons is much closer to 109.5^o.

Correct answer is option D

Chair >Twist boat > Boat > Half-chair 

above is the stability order of
the conformed.
Stability is inversely proportional to potential energy.

The correct answer is Option D.
Although conformers differ in potential energy and stability, the difference is so small that it does not allow their practical separation.

The correct answer is option A
Conformational isomers. Methane (CH₄) is a molecule that is a perfect tetrahedron, and so it is commonly said that no isomerism is possible with methane. However, the carbon-hydrogen bonds of methane constantly vibrate and bend, so that on very short timescales an apparent isomerism can be said to exist.

The correct answer is option D

This molecule is non-polar two Cl atoms in one carbon atom cancel the polarity other two Cl atoms on the next carbon.
Also all the Cl atoms are at max distance from each other so max. Stability due to less repulsion between Cl atoms. Dihedral angle between H and Cl is 60°

The correct answer is option C
Conformers are isomers having the same bond connectivity sequence and can be interconverted by rotation around one or more single (σ) bonds. Hence, the two structures represent conformers.