<p>[Just by unplugging your] cell phone charger when you are not using it reduces carbon dioxide pollution.</p>
<p>A. Just by unplugging your
B. Just unplugging one's
C. Just unplugging your
D. By just unplugging your
E. If you just unplug</p>
<p>The correct answer is C. I chose A. I wonder why is it so and what is the difference between A and C. </p>
<p>Last month a committee [created] [in response to] employee' [demands for] safer working conditions [has responded] a workshop on industrial safety. [No Error].</p>
<p>I thought A is wrong because it should be "is created" instead. However the correct answer is D. I don't understand why. </p>
<p>Though I am [acquainted with] Mr. Bartholomew and have [long known of] his interest in the painting, that he has gone to such lengths [to obtain it] [astonishes me]. [No Error]</p>
<p>I thought C is definitely wrong because of the ambiguity of the pronoun "it". However, the correct answer is No Error..Why?!!</p>