When she was a sophomore, though, she took a course in biology. 

    【答】这里的 though 是副词，常常放在句末，也可以放在句子中间，用逗号与句子的其它部分隔开，意思是 however (不过)。例如：

    Nice day. Yes. Bit cold , though. 天气不错。没错。不过有点冷。The strongest argument , though , is economic and not political . 不过，最强有力的论点是经济方面的，而不是政治方面的。（摘自《牛津英语用法指南》第三版 49.4）

though为副词，作连接性状语（conjunct)。连接性状语并不修饰本句，而是在意义上将本句和前一句连接起来（不是语法上）。即本句和前一句为转折关系。

(1)though用作连词 (conj.)conj. 虽然，尽管；即使；纵然

Though we have tried our best, we lost the game.
虽然我们已尽了最大的力量,但还是输了。

I don't know him well though I've known him for a long time.
我对他并不了解，虽然我认识他已经很长时间了。

Though the task was difficult,they managed to accomplish it on time.
尽管任务困难,他们仍按时完成了。

They will probably win, though no one thinks so.
他们可能会获胜，然而没有人这样认为。

(2)though用作副词 (adv.) 可是，不过;但是,然而

He said he would come, he didn't, though.
他说他要来，可是并没有来。

Our team lost. It was a good game though.
我们队输了，可是这也不失为一场好球。

I've a bit of headache. It's nothing much, though.
我有一点头痛，不过并不厉害。

It might be worth your while to go to court. This is tricky, though, and you'll need expert advice. 

对你来说这官司或许值得一打，不过这件事有点棘手，你需要专家的建议。