Some parts of a sentence have been jumbled up, and labelled P, Q, R and S. Select the option that gives the correct sequence in which these parts can be rearranged to form a meaningful and grammatically correct sentence.

Many retailers have invested

P. time and money into understanding its

Q. make them healthier so they can continue to be marketed

R. promotions work, and changing product ingredients to

S. complexity, refitting shops, trialling which healthier