Заполните пропуски в предложениях, используя выделенные слова.
1.accumulation, II. accumulate, III. accumulated
1. Fossil fuels were formed as a result of the ... of vegetable matter. 2. These fossil fuels are organic materials that ... in the geologic past. 3. Coal, for example, deposited from vegetable remains ... in swamp (болото) areas millions of years ago. 4. As is known, any natural ... of mineral of some volume in the Earth's crust is a mineral deposit.