Which of the following is correct regarding the pH scale?

The cytoskeleton of a cell is comprised of protein fibres that provide structural support and help maintain the shape of the cell.

These protein fibres include microfilaments, intermediate filaments, and microtubules.

Choice A. Carbohydrates is not the correct answer because carbohydrates are a type of macromolecule that provides energy to cells and are not a component of the cytoskeleton.

Choice B. Nucleic acids is not the correct answer because nucleic acids are macromolecules that store and transmit genetic information and are not a component of the cytoskeleton.

Choice C. Lipids is not the correct answer because lipids are a type of macromolecule that makes up cell membranes and are not a component of the cytoskeleton.

Viruses lack the essential machinery needed to reproduce by themselves.

In fact, viruses can only reproduce after infecting a living cell - a process called viral replication.

Once inside a living cell, viruses re-program the cell’s machinery to produce viral proteins and genetic material to make new copies of themselves.

Choice A, Bacteria, is not the correct answer because bacteria have their own metabolic pathways and can reproduce outside of a host cell.

Choice B, Protozoa, is also not the correct answer because protozoa are single-celled eukaryotes that have their own metabolic pathways and can reproduce outside of a host cell.

Choice C, Helminths, is not the correct answer because helminths are multicellular parasitic worms that have their own metabolic pathways and can reproduce outside of a host cell.