How do mosquitoes locate human beings to bite?

The correct option is D They use their sense of smell

• Many insects, mosquitoes included, are attracted by the odour of the carbon dioxide (CO2) gas that humans and other animals naturally exhale.
• However, mosquitoes can also pick up other cues that signal a human is nearby. They use their vision to spot a host and thermal sensory information to detect body heat.

So, the correct answer is 'They use their sense of smell'.