Which is the best example of a response to an external stimulus? drinking water after a long run
avoiding the sun by looking for food at night
a hungry bear hunting for food
falling asleep in the treetops of a forest

drinking water after a long run

Explanation:

When there arises a change or shift in the state or action of any organism because of any external stimulus, the result is said to be the response to external stimulus. The response or reaction to the external stimulus arises when the organism experiences or senses the stimulus.  

Drinking water after a long run is an example of the response to external stimulus. Here, the external stimulus is the loss of water in the water because of the action of running. This makes the individual drink water which is a response to the external stimulus.

The correct answer is A!

Explanation:

the dna molecules have a negative charge because of the phosphate groups in their sugar-phosphate backbone, so they start moving through the matrix of the gel towards the positive pole. power is turned on and dna fragments migrate through gel (towards the positive electrode).

explanation:

d. changes in climate and historical records

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