True a gerund can be the object of a preposition
Actually..... all of them are correct!
The difference is whether the word "the orchestra" needs a plural or singular verb. In American English a singular verb is needed (so American English would only accept options a) and c) ) but in British English both forms are acceptable: so in British English all four sentences are correct.
Answer:
your message have been given
WWhich two elements should be included with each visual aid in a technical document?