1. Statement (A):

The subsidiary quantum number $l$ is also called the azimuthal quantum number. It determines the shape of the orbital.

• $l=0 \Rightarrow s$ orbital
• $l=1 \Rightarrow p$ orbital
• $l=2 \Rightarrow d$ orbital

So, (A) is true.

2. Statement (B):

For a $2p_x$ orbital, the boundary surface diagram consists of two lobes oriented along the $x$-axis with a nodal plane at the $yz$-plane.

The given figure is intended to represent the boundary surface diagram of the $2p_x$ orbital, so (B) is true.

3. Statement (C):

In orbital wave functions, the signs $+$ and $-$ do not represent positive or negative charge. They indicate the phase (algebraic sign) of the wave function.

Therefore, (C) is false.

4. Statement (D):

For the $2p_x$ orbital, the angular part is proportional to $x$. Hence the wave function becomes zero when $x=0$.

The plane $x=0$ is the $yz$-plane, not the $xy$-plane. So the wave function is zero everywhere in the $yz$-plane, not in the $xy$-plane.

Therefore, (D) is false.

5. Conclusion:

True statements are:

• (A)
• (B)

So the correct option is:

$\boxed{\text{A: (A) and (B) only}}$

6. Comparison with stored correct answer:

Stored correct answer = A

Our derived answer = A

Hence, they agree.