Correct answer: (d) 1, 2 and 3
Explanation
- A
1 only
(a) 1 only. Chlorophyll/vegetation indices from satellites are real, but greenhouse-gas sensing over rice paddies and land-surface temperature are also established remote-sensing products, so 1 only is not the key.
- B
2 and 3 only
(b) 2 and 3 only. Those two are valid uses, but dropping chlorophyll is incomplete, so this is not the key.
- C
3 only
(c) 3 only. LST is only one of the three listed applications, so 3 only is not the key.
- D
1, 2 and 3
(d) 1, 2 and 3. Optical indices estimate chlorophyll/vegetation greenness; microwave and other missions constrain methane and related fluxes from rice; thermal infrared gives land-surface temperature. All three uses are live, so this is the official key.
Summary. Official key is (d) 1, 2 and 3. Remote sensing is not only pretty pictures: vegetation chlorophyll, paddy-related greenhouse gases, and surface temperature are all retrieved from satellite sensors. Honour the stored letter (d).