Choice A is the correct answer. The width of a parabola is determined by the absolute value of the leading coefficient $|a|$.

• Smaller $|a|$$\rightarrow$ Wider graph.
• Larger $|a|$$\rightarrow$ Narrower graph.

Comparing values: $0.1 < 1 < 2 < 10$. So $0.1$ produces the widest graph.

Choice B is incorrect because $1 > 0.1$. Choice C is incorrect because $2 > 0.1$. Choice D is incorrect because $10 > 0.1$ (narrowest).