Correct option is B
The correct improvement for the highlighted part of the sentence
"Dinesh requested the lady at the counter to give him a seat besides the window" is
"a seat beside the window."
· "Beside" means next to, while "besides" means in addition to or also.
· The correct preposition for indicating location next to the window is "beside."
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Example: Please place the chair beside the table, similarly using "beside" to indicate proximity.