Step 1: Concept
Pressure ($P$) is defined as Force ($F$) divided by Area ($A$): $P = F/A$.
Step 2: Meaning
If pressure is the same, then $F \propto A$. For a circular syringe, Area $A = \pi r^2$.
Step 3: Analysis
$F_1/F_2 = A_1/A_2 = (r_1/r_2)^2 = (1/5)^2 = 1/25$.
Step 4: Conclusion
Hence, the forces acting are in the ratio 1:25.
Final Answer: (C)