Pick out the wrong statement.

• If sufficient residence time (around 8 seconds) is not proivided to the downcoming liquid in the downcomer, it may entrain some vapour.
• The liquid head in the downcomer should not be greater than one half the plate spacing to avoid flooding.
• The dischare end of the downcomer must project far enough into the tray liquid so that no gas bubbles can enter the open end and by pass the bubble caps.
• none of these.