Use the Following Information to Answer the Following Questions

question 49

Multiple Choice

Use the following information to answer the following questions.
In Drosophila after ~100 minutes postfertilization, the embryo looks like the following diagram, with all nuclei having moved to the periphery and, subsequently, four of the nuclei being sequestered at the posterior end.

Drosophila embryo after about 2 hours.
-At this point, the embryo is characterized as

• A) a first-stage larva.
• B) nuclei in the cortex that has not undergone cytokinesis.
• C) nuclei in the cortex forming a single-cell layer over the surface.
• D) an embryo with segmentation beginning to be apparent.

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Definitions:

Spontaneous Recovery

The reappearance of a previously extinguished conditioned response after a period of time without exposure to the conditioned stimulus.

Unconditioned Response

A natural, instinctive response to a stimulus that happens without any previous learning or conditioning.

Conditioned Stimulus

An initially neutral stimulus that, after being associated with an unconditioned stimulus, comes to trigger a conditioned response.

Operant Conditioning

A learning process in which the strength of a behavior is modified by reinforcement or punishment.