Companion cells load most of the carbohydrates into sieve tube members
a. through plasmodesmata.
b. by osmosis.
c. by antiport.
d. through carrier proteins.
e. by symport.
A
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Which of the following levels of ecological organization is arranged in the correct sequence from most to least inclusive?
A) community, ecosystem, organism, population B) ecosystem, community, population, organism C) population, ecosystem, organism, community D) organism, population, community, ecosystem E) organism, community, population, ecosystem
Each chromosome has one or more ________ site(s) where replication begins.
A. bifurcate B. origin C. promoter D. replicon
Which of the following statements about digestion is true?
A) Digestion occurs only in the stomach. B) Digestion can be both mechanical and chemical, and it occurs both in the mouth and in the stomach. C) Mechanical digestion occurs only in the stomach; chemical digestion occurs only in the mouth. D) Digestion is the same thing as ingestion.
Which of the following statements concerning B cell receptors (BCRs) is FALSE?
A) They are formed in response to an encounter with an antigen. B) They are complementary in shape to a specific antigenic determinant that they may or may not encounter. C) They are bound to the surface of B lymphocytes and have two antigen-binding sites. D) Each B lymphocyte is randomly generated with antibody variable regions that determine its BCR. E) Scientists estimate that each person forms at least 1011 different types of B lymphocytes with distinct BCRs.