Sieve-tube elements are food-conducting plant cells that are part of the
A) xylem.
B) tracheids.
C) phloem.
D) sclereids.
Answer: C
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Which structure of the brain contains the cerebral spinal fluid?
a. ventricles b. thalamus c. medulla d. meninges e. reflexes
The head of a sperm is capped with an organelle that contains glycoprotein-digesting enzymes. What is this organelle called?
A. zona pellucida B. acrosome C. granulosa D. blastula E. neural cap
The taxonomic grouping that would represent the next highest (more inclusive) level above that
represented in Figure 23-1 is: a. Family. b. Order. c. Class. d. Phylum. e. Kingdom.
Suppose you've assumed the following two data-generating processes: (1) Yi = f (Hi, Ji) and (2) Ji = g (Xi, Zi). What do these assumptions imply?
A. X has an indirect causal effect on J. B. J has a direct causal effect on H. C. Z has an indirect causal effect on Y. D. Z has a direct causal effect on Y.