Всё просто. Множ.число-these. Ед.ч-this. Much-неисч. Many-исч. (можно посчитать 2 ручки, 2 тетради, но нельзя-два дождя, два джема)
1) This\These boots are brown. 2) That\Those skirt is very nice. 3) This\These dress is new. 4) That\Those jeans are blue. 5) There is not\are not many \ muchjam on the table. 6) Is\Are therea lot of \ manyflowers in that \ those vase?