關於case的一道英語選擇題

題目：

關於case的一道英語選擇題
I've heard that our boss is to arrange for me to have a trade talk with another company,_____I can't go for a picnic with you on sundayA.in that case  B.in which case答案說是B,因爲是非限定性定語從句,但這要怎麼翻譯啊,加入用in that case（是固定短語,意爲如果是那樣的話）不是會翻譯的通嗎,

解答：

另起一句話的話可以選A 也就是 I've heard that our boss is to arrange for me to have a trade talk with another company.In that case I can't go for a picnic with you on sunday.
在從句中的話要用which,用來指代前面的主句.
否則的話就成了用逗號連接兩個獨立的句子,那樣是明顯不對的.