Which of the following is NOT true of tonus?

A) It is a state of slight muscle contraction.
B) It occurs when a muscle is fully contracted.
C) During periods of tonus, the motor units take turns contracting.
D) It keeps the motor units healthy and ready to contract at any time.
E) All of these are true of tonus.

In angiosperms, water flows lengthwise through tracheids by moving through ____ and lengthwise through vessel elements by moving through ____. sieve plates; perforation plates

A) pits; sieve plates
B) pits; perforation plates
C) sieve plates; perforation plates
D) sieve plates; pits
E) perforation plates; pits