<p>The correct answer is <strong>(B) increasing</strong>.</p><p><span style="font-size: 13.008px;">The key preposition here is "by." The word "by" is often followed by a gerund, which is the "-ing" form of a verb. This is because a gerund functions as a noun and is used to indicate the means or method by which something is done. So, the answer is </span><span style="font-size: 13.008px;"> </span><span style="font-size: 13.008px;">(B) increasing </span><span style="font-size: 13.008px;">- This is the gerund or "-ing" form of the verb. This form can act as a noun and, as such, can follow the preposition "by" to indicate the method or means of action.</span><span style="font-size: 13.008px;"> </span></p>