Final answer:
The subject in the sentence 'He showed Ah Ma how to do a cannonball off the diving board.' is 'He.' It's the person who is performing the action, showing how to do a cannonball.
Step-by-step explanation:
In the sentence 'He showed Ah Ma how to do a cannonball off the diving board,' the subject is 'He.' The subject of a sentence is the person, place, thing, or idea that is doing or being something. In this case, 'He' is the one doing the action, which is showing Ah Ma how to do a cannonball. Understanding the concept of subject in a sentence is vital in understanding sentence structure in English.
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