The parents just (plant) flowers.1 have been planting2 have planted3 planted​

have planted

2 have planted , я подтвердил

"Many" используется только с исчисляемыми существительными во множественном числе, то есть с объектами, которые посчитать можно. Many cars, many bottles.

Much используется с неисчисляемыми существительными в единственном числе, то, что посчитать в принципе нельзя: Much water, much bread, much money.

A lot of/lots of можно использовать и в том и в том случае, это более неформальный и разговорный вариант, и дословно переводится как "полно" каких то объектов There are a lot of people near the museum.

A lot можно перевести как "очень часто" или "очень сильно" - She likes it a lot   

Nowadays, a great (41) …variety……… of different food is available VARY

from large supermarkets. There are rarely any (42) …shortage……. of SHORT

fresh food, and there is far less (43) …likelihood……. of our having LIKELY

to rely on (44) …frozen……. products. Does this mean that supermarkets FREEZE

have become the most (45) …successful…….. shops of all time? Certainly SUCCESS

they seem to have made some kinds of food less (46) …expensive…. and EXPENSE

most people enjoy shopping in them. There has been a (47) …reduction.. REDUCE

in the number of (48) …complaints……. made against supermarkets in recent COMPLAIN

years. The assistants are no longer (49) ……impolite….., but smile and try to be POLITE

helpful. Above all, supermarkets have shown a (50) …willingness……. to listen WILLING