The Earth has experienced ____ major mass

extinctions during its history.



a. 3
b. 5
c. 8
d. 12
e. 15


B

Biology & Microbiology

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Which of the following mechanisms is used by retrotransposons?

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DNA is characterized by which of the following feature(s)?

A. Ribose B. Single-stranded C. Deoxyribose D. Thymine E. Deoxyribose AND thymine

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Photosynthesis takes place mainly in the

a. stomata. b. vascular bundles. c. cuticle. d. lower and upper epidermis. e. mesophyll tissue.

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