Read the following passage carefully and choose the most appropriate answer to the question out of the four alternatives. In short, to write a good letter you must approach the job in the lightest and most casual way. You must be personal, not abstract. You must not say, 'This is too small a thing to put down'. You must say, 'This is just the sort of small thing we talk about at home. If I tell them this they will see me, as it were they'll hear my voice, they'll know what I'm talking about'. That is the purpose of a letter. Carlyle had the trick to perfection. He is writing from Scotsbrig to his brother Alec in Canada and he begins talking about his mother. Good old Mother, he says, 'she is even now sitting at my back, trying at another table to write you a small word with her own hand; the first time she has tried such a thing for a year past. It is Saturday night, after dark; we are in the east room in a hard, dry evening with a bright fire to our two selves; Jenny and her Barns are 'scouring up things' in the other end of the house; and below stairs the winter operations of the farm go on, in a subdued tone; you can conceive the scene! How simple it is and yet how perfect. Can not you see Alec reading it in his far-off home and his eyes moistening at the picture of his old mother sitting and writing her last message to him on earth? Subdued tone means _______.