The correct option is A that she has left the office - object
A noun clause is a dependent clause that functions as a noun. It usually
begins with what, whatever, whom, that and other such relative
pronouns. A noun clause can act as a subject, object, predicate
nominative or object of a preposition, in a sentence.
The noun clause
"that she has left the office" functions as the object of the verb
"told" in the given sentence. Hence option B is correct.
Option A is incorrect; it isn't a noun clause as it contains the main verb "told".
Option C is incorrect because the clause is the direct object here, the indirect being "me".
Option D is incorrect because it is a fragment of the noun clause and it isn't the subject. The subject of the sentence is "she".