The double implication "if and only if" is graphically represented by an arrow pointing in both direction, so the correct writing is

B!
hope this helps, it just seems like the best answe.
Answer:
ok so if the bird is on the top at 15 and a half then goes down six feet substrate 15 and a half from six and you get nine and half from the ground to the bird
Step-by-step explanation:
ans=26.92
use trigonometric ratios
a²= b²+c²
a²=25²+10²
a²=625+100
now take square root on both sides
a

a=26.92
a=27 (2decimal place)
Answer: Direction opens downward
Step-by-step explanation:
X-Intercept: (1/14,0),(-1/4,0)
Y-Intercept: (0,1)
Find the vertex using x= -b/2a
Plug it into the vertex form = y=a(x-h)^2 +k
H,K will identify the direction.