B. 1/9
Step-by-step explanation
The probability of an event is the number of favorable outcomes divided by the total number of outcomes.

Step 1
Let A represents the event that the birds lands between b and c
a)so, in this case the favorable outcome is that the birds lands between b and c, the length bewtween b and c is

and , the total outcome is the total lengt, so total outcome = AD

b) now,replace in the formula

therefore, the answer is
B. 1/9
I hope this helps you