Sometimes, the brilliant rays of light spread upward in the shape of a fan. 17 , they flash here and there like giant searchlights.
答案：(B) At other times
At other times 意為「在其他時候」，與前一句句首的 Sometimes 呼應：極光有時像扇形向上散開，有時則像巨大探照燈四處掃射；At one time（曾經）、At all times（隨時）、At the same time（同時）都無法構成這組呼應。
答對率 39%。
四個選項都以 At 開頭，字面都跟時間有關，只能靠與前一句的呼應關係判斷。
Sometimes, the brilliant rays of light spread upward in the shape of a fan.（有時候，明亮的光束呈扇形向上散開）——句首用了 Sometimes，本句自然要用 At other times（在其他時候）來承接。「Sometimes… At other times… 是英文描述「兩種交替出現的情況」最固定的一組搭配」，同義的還有 Sometimes… Other times…、At times… At other times…。這一格必須讀前一句才選得出來。
At one time 是「曾經、一度」，指過去某段時期；At all times 是「隨時、always」；At the same time 是「同時」——但極光不會同時呈扇形又四處掃射，前後矛盾。
Sometimes… At other times…（有時…有時…）、at one time（曾經、一度）、at all times（隨時）、at the same time（同時）、at times（有時）。
The northern lights, known as the aurora borealis, is one of nature's most dazzling spectacles. Science is still not certain 16 exactly what these lights are and what causes them.
Sometimes, the brilliant rays of light spread upward in the shape of a fan. 17, they flash here and there like giant searchlights. Farther north, the aurora frequently looks like fiery draperies which hang from the sky and sway 18 while flames of red, orange, green, and blue play up and down the moving folds.
According to scientific measurements, this discharge of light 19 from 50 to 100 miles above the earth. It is seen 20 around the Hudson Bay region in Canada, in northern Scotland, and in southern Norway and Sweden.