List the advantages of natural gas

Why is $\mathrm{CNG}$ preferred as a fuel?

Write the quadrants in which the following points lie:

$\left(-4,7\right)$

Read the following passage and answer the question.
Ali noticed that thick, black smoke was coming out from his school bus. He met the transport in-charge and convinced him to get the bus checked for harmful gases emission.

Suggest an environment-friendly fuel for this bus.