Which of the following can work as error detecting devices?
1. A pair of potentiometers
2. A pair of synchros
3. A differential transformer
4. An amplidyne

5. A control transformer

Select the correct answer using the following codes:
(a) 1, 2 and 5
(b) 2, 3, 4 and 5
(c) 1, 3, 4 and 5
(d) 1, 2, 3 and 4.