A

Step 1: Understand the behavior of an LC circuit. An LC circuit consists of an inductor (L) and a capacitor (C) that are connected together.
Step 2: Analyze the assertion. The charge on the capacitor in an LC circuit does indeed oscillate in a simple harmonic manner due to the exchange of energy between the electric field stored in the capacitor and the magnetic field in the inductor. This oscillation can be described by the equation of simple harmonic motion.
Step 3: Now, consider the reason. The total energy in an LC circuit is conserved, meaning that it remains constant over time. The energy oscillates between the electric energy in the capacitor ($\frac{1}{2}CV^2$) and the magnetic energy in the inductor ($\frac{1}{2}LI^2$), but the total energy does not change.
Step 4: Assess the relationship. Since the total energy conservation leads to the oscillation of charge, the reason provides a correct explanation for the assertion.
Therefore, both the assertion and reason are true, and the reason correctly explains the assertion. Thus, the answer is Option A.