Answer:
a) always
Step-by-step explanation:
We have been given that three corresponding sides of one triangle are proportional to three sides of another, then the triangles are similar. We are asked to choose the correct choice about our given statement.
We know that when three corresponding sides of one triangle are proportional to three sides of another triangle, then the both triangles are always similar.
Therefore, the correct choice is always and option 'a' is correct.