ANS:A - parabola (vertex being at the opening).

The path followed by a water jet issuing from the bottom of a water tank will be a parabola.

Explanation:

1. Projectile Motion:
   • When water is ejected from the bottom of a tank, it moves under the influence of gravity and the initial velocity imparted by the pressure at the exit point.
   • This motion can be described as projectile motion, where the trajectory follows a parabolic path.
2. Characteristics of Parabolic Path:
   • A parabola is defined by the equation y=ax2+bx+cy = ax^2 + bx + cy=ax2+bx+c, where yyy and xxx are coordinates and a,b,ca, b, ca,b,c are constants.
   • In projectile motion, the water jet follows a parabolic path with the vertex (highest point) at the point of exit from the tank (assuming ideal conditions and neglecting air resistance).
3. Other Options Analysis:
   • Hyperbola: Typically not associated with projectile motion under gravity; it describes a different geometric shape unrelated to this scenario.
   • Horizontal Straight Line: Implies no vertical component of motion, which is not the case here as the water jet will have both vertical and horizontal components.
   • Zig-zag Path: This term suggests an erratic or unpredictable path, which does not describe the predictable trajectory of a water jet under gravity.

Conclusion:

Therefore, the correct geometric description of the path followed by a water jet issuing from the bottom of a water tank, under the influence of gravity, is a parabola. This trajectory is a result of the combination of initial velocity and gravitational acceleration acting on the water jet.