题目

Like any good machine, the brain needs a little care and attention as it ages to ensure it continues to run in good working order. 【1】.Don't lose faith in your abilitiesAs people get older, it's easy to assume that your memory is already fading. In fact, 【2】. So if you do find yourself hesitating in a doorway not really knowing where you are meant to be, just see it as a reminder to push your memory a little bit harder.Learn a language or a musical instrument【3】， such as learning the piano or picking up a new language. Both rely on a wide skill set, exercising your memory, attent对于灯泡来说，电流在灯丝中无论沿什么方向流动都能发光．但是用半导体材料做成的二极管只能让一个方向的电流流过它（即单向导电性，二极管的符号类似一个箭头，电流方向与箭头方向相同时，电流才能通过）．如图所示灯泡发光，可知道电池的左边是______极，右边是______极（填“+”、“-”），导线中电流方向为______→______→______（填“A”、“B”、“C”）．