If $A$ be the set of triangles in a plane and $R^{+}$ be the set of all positive real numbers, then the function $f\::\:A\rightarrow R^{+},$ defined by $f(x)=$ area of triangle $x,$ is
Hence, option$(C)$ is the correct answer.
@`JEET how do you know that area of triangles in the plane will cover all the positive real numbers.
i.e Do you have a proof that Range = R+