Quick approach:
We are tryna find the area of triangle ABC
1) one side's length of Triangle ABC is 3, the other's length is 4
This means that 1 < x < 7, we could draw many different triangles that fits this inequality, where we would get different areas. There's no need to calculate anything, once you see the previous mentioned analysis we can eliminate this answer choice
2) Triangle ABC is a right triangle
This gives us the type of triangle we're looking for, but we don't know anything about the sides of the triangle, therefore eliminate this answer choice as well
1/2) We know that one side = 3, other = 4, and last side = 1 < x < 7 (where x is the last side)
Let's create 2 right triangles
Triangle 1: this Right Triangle is in the form of 3:4:5 (where 3 and 4 are the legs, and 5 is the hypotenuse) this would give us an area of 6 (since 12/2 = 6)
Triangle 2: this Right Triangle is in the form of 3:√7:4 (where 3 and √7 are the legs, and 4 is the hypotenuse), notice that this would give us a totally different area which is not equal to 6 (our previous triangle)
Since we got 2 different values and not 1 unique value, our answer will be E