The slant height is read from the diagram as 20.1 km.
The radius is half the diameter, so is 9.0 km.
The lateral area is ...
A = πrs = π(9.0 km)(20.1 km) ≈ 568.3 km²
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Desmos uses r for a special purpose, so we have used r₁ to signify the radius of the cone. The "round" function works only to round to an integer, so special effort must be used to get rounding to 1 decimal place.
The answer is A. When 0.7 is put into fraction form it turns into 7/10. Then change the denominator of 3/5 to 10 which makes it 6/10. 7/10 is higher than 6/10 so the answer is A.