The
steady state stability of the power system can be improved by
Using
machines of high impedance
Connecting
transmission lines in series
Connecting lines in parallel
Reducing the excitation of the machines
Connecting lines in parallel
Steady
state stability 
By
using bundle conductors or double circuit lines, the reactance is reduced than
single circuit line. Hence steady state stability limit increases.
Hence,
the correct option is (C).
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