Which two statements are true about RED?

Which two statements are true about RED? (Choose two.)

A.
RED randomly drops packets before the queue becomes full.

B.
RED is always useful, without dependency on flow.

C.
RED increases the drop rate as the average queue size increases.

D.
RED has a per-flow intelligence.

Explanation:
RED aims to control the average queue size by indicating to the end hosts when they should
temporarily slow down transmission of packets.
RED takes advantage of the congestion control mechanism of TCP. By randomly dropping
packets prior to periods of high congestion, RED tells the packet source to decrease its
transmission rate. Assuming the packet source is using TCP, it will decrease its transmission rate
until all the packets reach their destination, indicating that the congestion is cleared. You can use
RED as a way to cause TCP to slow down transmission of packets.
TCP not only pauses, but it also restarts quickly and adapts its transmission rate to the rate that
the network can support.
RED distributes losses in time and maintains normally low queue depth while absorbing spikes.
When enabled on an interface, RED begins dropping packets when congestion occurs at a rate
you select during configuration.
Packet Drop Probability

The packet drop probability is based on the minimum threshold, maximum threshold, and mark
probability denominator.
When the average queue depth is above the minimum threshold, RED starts dropping packets.
The rate of packet drop increases linearly as the average queue size increases until the average
queue size reaches the maximum threshold.
The mark probability denominator is the fraction of packets dropped when the average queue
depth is at the maximum threshold. For example, if the denominator is 512, one out of every 512
packets is dropped when the average queue is at the maximum threshold.

http://www.cisco.com/en/US/docs/ios/12_2/qos/configuration/guide/qcfconav.html