Final Answer:
It determined by the properties of midpoints in triangles. Therefore the correct option is C. 70
Step-by-step explanation:
The perimeter of ABC can be determined by recognizing that the midpoints of a triangle's sides create smaller triangles that are similar to the original triangle.
This means the ratio of the perimeter of the smaller triangle to the larger triangle is 1:2. Given that d, e, and f are midpoints, the perimeter of ABC is twice the perimeter of def.
If def is a smaller triangle compared to ABC, its perimeter can be calculated by summing the lengths of its sides, which are half the lengths of the corresponding sides of ABC. So, if the perimeter of def is 35, then doubling that gives us the perimeter of ABC as 70.
Therefore the correct option is C. 70