Which of the following is an example of a liquid conductor?

The answer is correct because body fluids and alkali solutions are both examples of liquid conductors. These substances contain ions that facilitate the flow of electric current. Body fluids such as blood and interstitial fluid have electrolytes, which dissociate into charged particles, allowing the conduction of electricity. Similarly, alkali solutions, which often contain hydroxide ions (OH-) and metal cations, also show good conductivity due to their ionic composition.

In contrast, neon is a noble gas and does not conduct electricity in its gaseous state, while plastics and rubber are typically insulators and do not allow electric current to flow through them. Insulating materials like plastics and rubber are specifically designed to prevent the passage of electrical currents, thus making them unsuitable examples of conductors.