Task 2
Directions: This task is the same as Task 1. The 5 questions or unfinished statements are numbered 41 through 45.
Why don't birds get lost on their long flights from one place to another？ Scientists have puzzled over this question for many years. Now they are beginning to fill in the blanks.
Not long ago, experiments showed that birds depend on the sun to guide
The reason why birds don't get lost on long flight ______.

A. has been discovered recently
B. is known by everybody
C. still remains a mystery
D. has been known to scientists for years