7. The second vaccination is beneficial because it
(A) contains mast cells that survive longer than 4-5 days.
(B) stimulates production of a higher concentration of antibodies in the bloodstream.
(C) requires two injections to stimulate antibody formation.
(D) keeps previously produced cytotoxic T cells circulating in the bloodstream.

3. RNA interference (RNAi) can be used by (A) researchers to induce the production of more mRNA. (B) researchers to artificially turn on gene expression. (C) viruses to stop the production of new proteins. (D) cells to prevent infections from double-stranded RNA viruses.

4. Sympatric speciation commonly occurs through_______ in plants but is more likely to occur through_______ in animals. (A)polyploidy； habitat differentiation and sexual selection (B) habitat differentiation and sexual selection； polyploidy (C)asexual reproduction；chromosome duplications (D) self-pollination； polyploidy and other genetic mechanisms 

5. Mycorrhizal fungi are sometimes purposely introduced to new areas of land that are used for growing plants for commercial uses (e.g., landscaping, crop production, timber production). What would be the benefit of doing this? (A) The fungi absorb toxic pesticides from the ground. (B) The fungi help facilitate horticulture, agriculture, and forestry. (C) The fungi promote the evolution of new fungus species. (D) The fungi prevent competitive plant species from growing.

6. Homeostasis (A) is the maintenance of a relatively constant internal state. (B) results from hormone imbalance. (C) occurs when the external environment changes to match the internal environment. (D) is the way the internal environment influences the external environment.

8. Our biological clock, which regulates the sleep-wake cycle, is housed within the (A) cerebrum. (B) hypothalamus. (C) cerebellum. (D) brainstem.

9. Which statement regarding compound eyes is TRUE? (A) They have one light-focusing lens. (B) They are poor motion detectors. (C) They can provide excellent color vision. (D) They can perceive only visible light.

10. Which of the following biomes is characterized by mild, rainy winters and hot, dry summers? (A) Tropical forest (B) Temperate grassland (C)Savanna (D) Temperate seasonal forest (E) Mediterranean woodland and shrubland

11. A child dies following a series of chronic bacterial infections. At the autopsy, the physicians are startled to see that the child's white blood cells are loaded with vacuoles containing intact bacteria. Which explanation could account for this finding? (A) A defect in the Golgi apparatus prevented the cells from processing and excreting the bacteria. (B) A defect in the rough endoplasmic reticulum prevented the synthesis of the antibodies (defensive proteins) that would have inactivated the bacteria. (C) A defect in the cell walls of the white blood cells permitted bacteria to enter the cells. (D) A defect in the lysosomes of the white blood cells prevented the cells from destroying engulfed bacteria.

12. Two chromosomes in a nucleus that carry genes controlling the same inherited characteristics are (A) homologous chromosomes. (B) sister chromatids. (C) complementary chromosomes.

13. Why is a guide RNA needed when using CRISPR-Cas9 for gene editing? (A) to help Cas9 be transported into the nucleus (B) to help Cas9 find the target DNA to cut (C) to help repair the target DNA after it is cut (D) to help make copies of the target DNA