31. In the past few years, research has suggested that Vitamin D may increase the level of serotonin（血清素）, one of the key neurotransmitters influencing our mood, and ________it helps to relieve mood disorders.
| A．that | B．where | C．what | D．Which |
Dress warmly, _____ you'll catch cold.
| A．on the contrary | B．or rather | C．or else | D．in no way |
This book gives a brief _____ of the history of the castle and details of the art collection in the main hall.
| A．outline | B．reference | C．article | D．outlook |
How can we get this language point _____ to the students.
| A．down | B．round | C．across | D．into |
I got out of the taxi, ___ the fare and dasked into the station.
| A．paying | B．paid | C．to pay | D．having paid |
I got out of the taxi, ___ the fare and dasked into the station.
| A．paying | B．paid | C．to pay | D．having paid |