Answer: 4 feet (approx)
Explanation:
Since, We know that the length of pendulum,

Where L is the length of pendulum
T is the period,
And, g is the gravitational acceleration.( g=9.8
)
Here, T= 2.2 seconds
Thus, Length of pendulum,
= 1.20268570733 meter
1 meter= 3.28 ( approx)
Thus L= 1.20268570733 ×3.28 feet =3.94480912005 feet ≈4 feet