Correct option is B
The statement by the environmentalist mentions that a high percentage of carbon dioxide increases the greenhouse effect. However, the statement does not imply that there should be minimum carbon dioxide in the environment (Assumption 1), nor does it suggest that a minimum greenhouse effect should be maintained (Assumption 2). The statement is merely describing the consequence of a high level of carbon dioxide but does not directly make any recommendation about maintaining minimum levels of either. Hence, neither assumption (1) nor (2) is implicit.