Answer:
elastic and gravitational
Step-by-step explanation:
Mechanical energy is the sum of the kinetic energy and potential energy of an object:

where

is the kinetic energy of the object (with m being the object's mass and v is the object's speed),
while U is the potential energy. Potential energy refers to the position of the object, and it can be of two types:
- Gravitational potential energy:
, where g is the gravitational acceleration and h is the height of the object above the ground
- Elastic potential energy:
, where k is the spring constant and x is the compression/stretching of the spring.
Therefore, the correct choice is:
elastic and gravitational