No doubt, the 'green revolution' has led to self-sufficiency in food production but it has also brought with it the formidable problem of poisoning of food grains and other eatables. This is caused by excessive use of chemicals on crops and pesticide residues. It has also created havoc by exterminating the species of useful parasites and viruses which keep pests under control. Scientists are now worried about the resurgence of such formidable pests in menacing proportions which seem to undermine all that they have achieved in agricultural production.
Which one of these phrases best helps to bring out the precise meaning of ' menacing proportions?

Options

A. To an extent which becomes threatening
B. Assuming dimensions that cause concern
C. Unimagined, dangerous proportion
D. Harmful size