Answer:
Option B is the correct answer.
Explanation:
Total distance traveled = 60 + 60 = 120 m
Time taken to walk across [tex]=\frac{60}{2}=30s[/tex]
Time taken to run back [tex]=\frac{60}{6}=10s[/tex]
Total time taken = 30 + 10 = 40 s
Average speed = Total distance traveled / Total time taken
Average speed [tex]=\frac{120}{40}=3m/s[/tex]
Option B is the correct answer.