In a play, a long speech by a single character in the presence of other characters is called:

B. monologue

A monologue is a speech delivered by one character, and it is typically addressed to other characters on stage or to the audience. This is different from a soliloquy, which is a speech where a character speaks their thoughts aloud when alone on stage. An aside is a brief remark made by a character to the audience, unheard by other characters on stage. A prologue, on the other hand, is an introductory section of a play or literary work.