Consider the following statements : The transient stability of the power system under unbalanced fault conditions can be effectively improved by 1. Excitation control 2. phase-shifting transformer 3. single-pole switching of circuit breakers 4. increasing the turbine input. Of these statements

Consider the following statements : The transient stability of the pow

1.	Consider the following statements : The transient stability of the power system under unbalanced fault conditions can be effectively improved by 1. Excitation control 2. phase-shifting transformer 3. single-pole switching of circuit breakers 4. increasing the turbine input. Of these statements
A.	1 and 2 are correct
B.	2 and 3 are correct
C.	3 and 4 are correct
D.	1 and 3 are correct
Answer» D. 1 and 3 are correct