Please help, correct answers only, will give brainliest.

Which strategy is an example of how companies may upgrade themselves to meet changing customer preferences? a.doing door-to-door sellingb.using billboards to advertise the productsc. making online shopping services availabled.giving discounts on products

Select the correct answer from each drop-down menu. in an experiment, dr. travis examined the effects of calcium intake on osteoporosis, a condition that causes an increased risk of bone fractures. the amount of calcium is variable. the risk of bone fractures .

Ecologist have observed a sharp increase of sulfur dioxide in the air . what might be a possible consequence of excessive sulfur dioxide in the air ? a. acid rain b. ozone layer depletion c.ozone layer hole d.increase in sea levels