Question

bacteria and viruses are alike in that theyre both so small that they can be seen only under a microscope. the two can cause infections with similar symptoms, such as fever, coughing, sneezing, vomiting, and fatigue—all of which are ways that the immune system tries to remove these microorganisms. however, important differences exist between the two. most bacteria are harmless; fewer than one percent make people sick. by contrast, most viruses do cause disease, and they attack specific cells. for example, some viruses target cells in the blood, the liver, and the respiratory system. other viruses even attack bacteria. unlike bacteria, viruses cannot survive without a host. in fact, they can only reproduce by attaching themselves to cells.

Explanation:

• "Can only be seen with a microscope": The text states "Bacteria and viruses are alike in that they're both so small that they can be seen only under a microscope", so both should check this box.
• "Can cause infections": The text says "The two can cause infections with similar symptoms", so both should check this box.
• "Most are harmless": The text mentions "Most bacteria are harmless; fewer than one percent make people sick. By contrast, most viruses do cause disease", so only bacteria should check this box.
• "Attack specific cells": The text says "most viruses do cause disease, and they attack specific cells", so only viruses should check this box.
• "Can survive without a host": The text states "Unlike bacteria, viruses cannot survive without a host", so only bacteria should check this box.

Answer:

• Can only be seen with a microscope: Viruses (☑), Bacteria (☑)
• Can cause infections: Viruses (☑), Bacteria (☑)
• Most are harmless: Viruses ( ), Bacteria (☑)
• Attack specific cells: Viruses (☑), Bacteria ( )
• Can survive without a host: Viruses ( ), Bacteria (☑)