Which of the following is the equation of a direct variation that has a constant of variation equal to -1/2?

A. y= x- 1/2
B. -1/2 y=x
C. y= -2x
D. y= -1/2x

The figure shows triangle def and line segment bc, which is parallel to ef: triangle def has a point b on side de and point c on side df. the line bc is parallel to the line ef. part a: is triangle def similar to triangle dbc? explain using what you know about triangle similarity. part b: which line segment on triangle dbc corresponds to line segment ef? explain your answer. part c: which angle on triangle dbc corresponds to angle f? explain your answer. asap