Which word is missing in the text below?
(A) Spring
(B) Monsoon
(C) Snow melt
(D) Autumn
 The Tonle Sap remains relativelysmall for most of the year, measuringabout a metre in depth and coveringaround 2,700 km2.However, the river connected to thelake starts to swell during the............... season as water that flowsfrom the Mekong River reverses,helping to expand the Tonle Sap to anarea of up to 16,000 km2 with a depthof up to 9 metres.