Let me explain this,

We know in triangle with sides A,B and c

Difference of any two sides < Third side < Sum of any two sides

Now consider the triangle above,

The maximum value of the third side must be less 10, or else the triangle rule wont be applicable

Now if we consider the third side =10 (assuming maximum value)

then Area = 1/2 * base * Altitude

= 1/2 * 4 * 10 = 20

Now the minimum value of the third side must be greater than 2.

SO let us take the value of third side = 2

Then Area = 1/2 * 4 * 2 = 4.

Now the area of the triangle is either greater than 12 or less than 12

Hence the option is D. (The diagram in geometry section are not drawn to scale unless specified. Here it looks like right angle triangle but nothing is mentioned so we cannot assume.)

Let me know if you need further clarification

thank you very much.
now it is clear

Begin with side rule, 4+6=10 , 6-4=2, so 3rd side will fall between 2 to 10. If 3rd side is 3 , Area will be 6, QB is Greater. if 3rd side is 9, area will be 18, now quantity A is greater, hence ans is (D)