<p>The correct answer is <b>(B) modifying</b>.</p>
<p>In this sentence, the phrase "have difficulties in" is followed by a verb form called a gerund, which is a verb that functions as a noun and ends in -ing. The gerund form is used here because it is describing the action or process that the overseas branches are having difficulties with.</p>
<p>The options (A) "modify", (C) "modified", and (D) "modification" are not correct because they are not in the correct verb form. "Modify" is a base form verb, "modified" is a past tense verb, and "modification" is a noun form. None of these forms can function as a noun in this sentence.</p>
<p>Therefore, the correct answer is (B) "modifying" because it is the gerund form of the verb and functions correctly as a noun in the sentence.</p>