..... is a great form of exercise

[Englishlearner]

..... is a great form of exercise. (*) Walks (*) Walking (*) To walking (*) Walk

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This is a companion discussion topic for the original entry at https://english.best/questions/21308,___-is-a-great-form-of-exercise/

[Torsten]

The correct answer is Walking is a great form of exercise. You need the gerund ‘walking’ here as it serves as the subject.