D

Step 1: Understand that when a beaker (or any fluid container) is subjected to a constant acceleration, the surface of the liquid inside the beaker will tilt at an angle.
Step 2: In this case, the beaker is accelerating with an acceleration of $10 \, ext{m/s}^2$ to the right. The angle $\theta$ is given as $45°$.
Step 3: This tilting occurs because the effective gravity experienced by the liquid is modified due to the acceleration:
- The effective gravitational field becomes $g_{eff} = \sqrt{g^2 + a^2}$ where $g = 9.8 \text{m/s}^2$ and $a = 10 \text{m/s}^2$.
Step 4: Therefore, at any point along the surface, the pressure difference between points A and B can be expressed as:
$$ P_A - P_B = \rho g_{eff} \cdot H \sin(\theta)$$
where $H$ is the height of the liquid column and $\rho$ is the density of the liquid.
Step 5: Since $\theta = 45°$, we expect $P_A > P_B$ as higher pressure exists at the bottom of the column based on the principles of hydrostatics.
Thus, the conclusion that holds is represented in option D: All, since both valid relations regarding the internal pressure profiles and effective gravity are confirmed.