An indirect radar echo is caused by a reflection of the main lobe of the radar beam off the observer's vessel. Which of the following is NOT a characteristic of indirect echoes?

A
Their bearing is almost constant, even when the true bearing of the contact changes appreciably.
B
They always appear on a bearing of 90°From the true bearing of the contact.
C
The indirect echoes usually appear in shadow sectors.
D
When plotted, their movements are usually abnormal.
E