Does anyone know the right answer ?

 A

Explanation:

Karyotypes can be used to screen for and confirm chromosomal abnormalities such as Down's syndrome, and there are several different types of abnormalities which may be detected.

Answer;

-First class lever

The neck is a first class lever.

Explanation;

-A lever is a simple machine that uses an applied force to rotate a rigid rod about a fixed pivot point/fulcrum with the purpose of lifting a weighted load. There are three major classes of levers, each defined by the location of the applied force or effort in relation to the load or resistance and the fulcrum.

-A first-class lever has its fulcrum placed between the applied force and the load. An example of a first class-lever is a seesaw.