Which of the following messages sent by ATC to an aircraft in flight must be read back?
- descend to (altitude) 3.000 feet
- wind 240° , 15 knots, gusts 30 knots
- turn right heading 210
- reduce speed to 160 knots
- squawk 1723
- braking action poor
1, 2, 3, 5
all
1, 3, 4, 5
1, 3, 4, 5, 6