Biology

The size of the Covid-19 virus is typically measured in nanometers (nm), not kilobytes (KB), which is a unit of digital information. The virus is approximately 60-140 nanometers in diameter, so none of the given options are correct.

Dolphins are widely recognized as highly intelligent mammals due to their complex social behaviors, problem-solving skills, and advanced communication abilities, making option B the best answer.

Ultra microscopic viruses are responsible for causing measles, which is a viral infection. Malaria and cholera are caused by parasites and bacteria respectively, while mumps is also viral but less commonly referred to as caused by 'ultra microscopic viruses' in general context compared to measles.

Reflex actions in the head region are primarily controlled by the brain, specifically by cranial nerves and brainstem centers, rather than the spinal cord. The spinal cord mainly controls reflexes in the body below the head.

The cornea is the transparent front part of the eye that can be donated and transplanted to restore vision in patients with corneal blindness. Other parts like the conjunctiva, iris, and pupil are not typically donated for transplantation.

The normal range of red blood cells (RBCs) in men is approximately 4.5 to 6.2 million per microliter of blood, which matches option A. This range is widely accepted in human physiology for healthy adult males.

Insects that transmit diseases from one host to another are called vectors. They carry pathogens that cause diseases, making option B the correct answer.

Plasma is the liquid component of blood and is composed mostly of water, which makes up about 90-92% of its volume. This high water content allows plasma to transport nutrients, hormones, and waste products throughout the body.

Malaria primarily affects the liver and spleen because the parasite first multiplies in liver cells and later infects red blood cells, which are filtered by the spleen. These organs are crucial in the disease's pathology.

Ageusia is the medical term for the loss of the sense of taste. It specifically refers to the inability to detect flavors, distinguishing it from anosmia, which is the loss of smell.