Which of the following plays an important role in screening out harmful ultraviolet rays?
A. atmospheric oxygen
B. water
C. methane
D. ozone
D. ozone
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Which of the following statements about RNA polymerase in bacteria is INCORRECT?
A. It binds the promoter region of a gene. B. It is bound to a sigma factor during initiation of transcription. C. It synthesizes RNA. D. It catalyzes the addition of nucleotides to the 5?end of a growing RNA strand. E. It dissociates from the DNA at the terminator.
The glottis is ____ when swallowing and ____ when speaking
a. closed; open b. open; closed c. rigid; relaxed d. relaxed; rigid e. vibrating; closed
Thrush, a painful yeast infection of the mouth, throat and vagina, is caused by a member of the genus:a
Aspergillus b. Candida c. Claviceps d. Penicillium e. Psilocybe
Which structure do sea slugs use to feed on their prey?
A) nematocysts B) an incurrent siphon C) a radula D) a mantle cavity