The correct option is B will be too late
The context uses the adverb "otherwise" to indicate what else could happen. Thus, the context refers to a possible future consequence. Also, from the notes given with reference to the context we can infer that option B is the correct answer. It refers to a possible consequence in the future, "will bee too late".
A is incorrect as there is a missing auxiliary verb. Hence, this is grammatically incorrect.
C is incorrect as the alternative to creating ecological balance cannot possibly be a threat (without mentioning from whom the threat might be).
D is incorrect as this option does not give a contrast as a consequence.