The Earth has experienced ____ major mass
extinctions during its history.
a. 3
b. 5
c. 8
d. 12
e. 15
B
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Why is each element unique with respect to its chemical properties? Each element has a distinctive _____
A) atomic mass B) number of electrons C) number of protons D) number of neutrons E) radioactive property
Which of the following mechanisms is used by retrotransposons?
A. cut-and-paste transposition B. replicative transposition C. bacterial transduction D. transposition via an mRNA intermediate E. lysogeny
DNA is characterized by which of the following feature(s)?
A. Ribose B. Single-stranded C. Deoxyribose D. Thymine E. Deoxyribose AND thymine
Photosynthesis takes place mainly in the
a. stomata. b. vascular bundles. c. cuticle. d. lower and upper epidermis. e. mesophyll tissue.