Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct word or phrase that best fits each of the numbered blanks.
Traditionally, rural villages in Vietnam produced handicrafts (25)______ they were not busy with planting or harvesting crops. Over time, many villages developed the expertise to (26)______ specialized products and so particular villages became famous (27)______ such things as weaving, woodwork, lacquer work and metal products.
With industrialisation many villagers moved to the cities but not maintained their craft skills and networks to produce products for the city market, for example, craft villages make furniture, grow flowers or make utensils for the urban population. Other villages changed from making (28)______ crafts to producing different products desired by an industrialised society.
Traditionally, rural villages in Vietnam produced handicrafts (25)______ they were not busy with planting or harvesting crops.
A. where
B. when
C. how
D. why