[解析]B?C?作并列连词时,when/while用法较为特殊,二者区别是:while表两相对照;而when表突然?在那时,常见于be about to do...when和hardly...when等句型中? 考点二、表示原因的连词for/because/as/since 例3.He found it increasingly difficult to read, ___ his eyes...