Identify the essential element missing from the following topic sentence. Dora the Explorer is a children's program on Nickelodeon.
A.
concrete detail
B.
controlling idea
C.
limited topic
D.
a concluding idea

B.

controlling idea

Explanation:

the following key ideas correctly express the key sentence.

restate key idea: most people can learn to swim in ten short lessons.

restate key idea: the majority of water-accident victims require mouth-to-mouth breathing.

restate key idea: an empty, tightly closed gallon jug will support a tired swimmer.  

restate key idea: first aid is to prevent accidents as well as assist in rescue.

explanation: the key idea needs to have the same topic as the key sentence (drowning and safety).