Alright, in that case I'm going to have to go out on a limb here and say B.

I say go out on a limb because I can't derive any of the solutions exactly, but B is closest to my (likely faulty) approximation.

Since this is by far the most interesting question here, I'll lay out my reasoning below.

Since the area is increasing by 5 square meters per second at the beginning, I simply see how long the legs would be once the area is 5 and call it a second. Then the speed would be approximately that leg length per second. I expect this approximation to be low because the rate of change of area should increase with distance at constant speed, as I mentioned in the above comment.

An isosceles right triangle is half of a square with side length equal to the length of that triangles legs.

Because I want an area 5 isosceles right triangle, I know the square will have area 10.

From there I take the square root of 10, which is a little more than 3.16.

So, my approximate speed is 3.16 m/s.

If speed is constant it doesn't matter whether they're 4 meters from the angle or 4 kilometers from the angle, they should be moving around 3.16 meters per second.

That is closest to option B, at 3.2 m/s, so I chose that one.

🤞