Those who have
already attended a performance of the play have said that it is at once
exhausting because of its length and complexity but its clever plot is still
intriging.
(划线部分为but及以后)
不选:however it is intrguing in its clever plot
正确项: and intriguing because of its clever plot.
顺便求however的用法
还有这句中
at once放这是干什么用的
总觉得and intriguing 很奇怪,因为觉得应该是转折的语气