Platelets are similar to erythrocytes in that both structures do not contain a _________________. Platelets are similar to leukocytes in that both their primary functions involve ________________ the body.

• A. Plasma membrane; nourishing.
• B. Plasma membrane; protecting.
• C. Nucleus; nourishing.
• D. Nucleus; protecting.

Answer: (D)

Verified step by step guidance

1. Understand the structure of platelets and erythrocytes: Both platelets and erythrocytes (red blood cells) are unique in that they do not contain a nucleus. This is a key structural similarity between the two.
2. Consider the primary function of platelets and leukocytes: Platelets are involved in blood clotting, which is a protective mechanism to prevent excessive bleeding. Leukocytes (white blood cells) are primarily involved in protecting the body against infections and foreign invaders.
3. Identify the correct terms to fill in the blanks based on the structural and functional similarities: The first blank should be filled with 'nucleus' because neither platelets nor erythrocytes have a nucleus. The second blank should be filled with 'protecting' because both platelets and leukocytes are involved in protective functions.
4. Review the options provided: The options are 'Plasma membrane; nourishing', 'Plasma membrane; protecting', 'Nucleus; nourishing', and 'Nucleus; protecting'.
5. Select the correct answer based on the analysis: The correct answer is 'Nucleus; protecting', as it accurately reflects the structural similarity (lack of nucleus) and functional similarity (protective role) between platelets and erythrocytes, and platelets and leukocytes, respectively.