The new pen ____ I am using ____ is of high quality.A.which;it B.that;it C.with which;/ D./;

D.如果你的D项是/；/的话,就是选D了
（___ I am using）是后置定语修饰The new pen,省略了that或 which；因为直接可以说use the new pen,所以不用加with
若题中using换成writing：The new pen ____ I am writing ____ is of high quality.那就选C,因为write with the new pen,不能省掉with,固定搭配