Option 1 states that Exercise Kavach is a military exercise of the Indian Army only. This is incorrect because Exercise Kavach is a joint military exercise.

Option 2 states that Exercise Kavach is a joint military exercise involving the Indian Army and the Indian Navy only. This is also incorrect because Exercise Kavach involves more than just the Indian Army and the Indian Navy.

Option 3 states that Exercise Kavach is a joint military exercise involving the Indian Army, the Indian Navy, and the Indian Air Force only. This is also incorrect because Exercise Kavach involves another branch of the military.

Option 4 states that Exercise Kavach is a joint military exercise involving the Indian Army, the Indian Navy, the Indian Air Force, and the Indian Coast Guard. This is the correct statement because Exercise Kavach involves all four branches of the Indian military - the Army, Navy, Air Force, and Coast Guard.

In summary, Exercise Kavach is a joint military exercise involving the Indian Army, the Indian Navy, the Indian Air Force, and the Indian Coast Guard.