Speed from volume flow rate and cross-sectional area Steps:

• Volume of water V = mass / density = 10 kg / 1000 kg/m³ = 0.01 m³
• Volume flow rate Q = V / time = 0.01 m³ / 0.2 s = 0.05 m³/s
• Cross-sectional area A = π (diameter/2)² = π (0.05 m / 2)² ≈ 0.002 m²
• Speed v = Q / A = 0.05 m³/s / 0.002 m² = 25 m/s

Why C is correct:

• The continuity equation defines speed as volume flow rate divided by cross-sectional area, yielding 25 m/s.

Why the others are wrong:

• A underestimates flow rate by factor of about 4.
• B underestimates by factor of about 2.
• D overestimates by doubling the flow rate.

Final answer: C