Concept:
Different graphical techniques in control systems are associated with specific characteristic parameters.
• Root locus deals with breakaway and break-in points.
• Bode plot uses corner frequencies.
• Nyquist plot studies encirclement of the critical point.
• Signal flow graph represents transmittance relationships.
Understanding these associations is extremely important in control system analysis.
Step 1: Matching Root Locus Plot.
Root locus analysis studies movement of system poles as gain varies.
An important feature in root locus is:
\[
\text{Breakaway point}
\]
Thus:
\[
A \rightarrow II
\]
Step 2: Matching Bode Plot.
Bode plots are frequency response plots.
The frequencies where slope changes occur are called:
\[
\text{Corner frequencies}
\]
Hence:
\[
B \rightarrow I
\]
Step 3: Matching Nyquist Plot.
Nyquist stability criterion depends on encirclement of:
\[
(-1+j0)
\]
which is called the:
\[
\text{Critical point}
\]
Therefore:
\[
C \rightarrow III
\]
Step 4: Matching Signal Flow Chart.
Signal flow graphs describe system variable relationships using:
\[
\text{Transmittances}
\]
Hence:
\[
D \rightarrow IV
\]
Step 5: Writing the complete matching.
Thus:
\[
A-II,\quad B-I,\quad C-III,\quad D-IV
\]
Hence the correct option is:
\[
\boxed{(4)}
\]