未知题型 ___________ the earth to be flat, many feared that Columbus would fall off the edge of the earth.A) Having believed B) Believing C) Believed D) Being believed

未知题型 I have kept that portrait ____________ I can see it every day, as it always reminds me of my university days in London.A) which B) whereC) whether D) when

未知题型 It is quite necessary for a qualified teacher to have good manners and _________ knowledge.A) extensive B) expansiveC) intensive D) expensive