question_answer

Consider the following statements:

1. Round bar in a round hole forms a turning pair.

2. A square bar in a square hole forms a sliding pair.

3. A vertical shaft in a foot-step bearing forms successful constraint.

Which of these statements are correct?         

A) 1 and 3            

B) 1 and 2                                

C) 2 and 3            

D) 1, 2 and 3