Average speed = total distance / total time in SI units Steps:

• Convert time to seconds: 21 h × 3600 s/h + 40 min × 60 s/min = 75,600 s + 2,400 s = 78,000 s.
• Convert distance to meters: 17,000 km × 1,000 m/km = 17,000,000 m.
• Calculate speed: 17,000,000 m / 78,000 s ≈ 218 m/s.
• Express scientifically: 218 m/s = 2.18 × 10² m/s ≈ 2.2 × 10² m/s (assuming option C notation aligns).

Why C is correct:

• It equals the average speed from distance/time formula, approximately 220 m/s after unit conversions.

Why the others are wrong:

• A: Too slow; equates to walking speed, not aircraft.
• B: Too fast by factor of 10; overestimates by ignoring full time conversion.
• D: Absurdly fast; exceeds escape velocity, impossible for aircraft.

Final answer: C