Final answer:
The electromagnetic force keeps molecules in a fluid together.
Step-by-step explanation:
The force that keeps molecules in a fluid together is the electromagnetic force.
This force is responsible for the attractions between the positively charged atomic nuclei and the negatively charged electrons in the atoms that make up the molecules.
For example, in water (H2O) molecules, the oxygen atom attracts the hydrogen atoms through electromagnetic forces, creating a cohesive force that keeps the molecules together.
Learn more about The force that keeps molecules in a fluid together