Which of the following is TRUE? A. a. Global warming was discovered in the twentieth century. B. b. French scientist Jean-Baptiste Fourier compared Earth’s atmosphere to the glass of a greenhouse in the beginning of the 18th century. C. c. Irish scientist John Tyndall discovered in the 19th century that water vapor is a heat-trapping gas involved in the greenhouse effect. D. d. In the 1890s, Swedish scientist Svante Arrhenius and American scientist P.C. Chamberlain suggested that water vapor in the air could cause problems for the planet.