Consider the following statements:Statement I: Some rare earth elements are used in the manufacture of flat television, screens and computer monitors,Statement II: Some rare earth elements have phosphorescent properties.Which one of the following is correct in respect of the above statements?

1. A

   Both Statement I and Statement II are correct and Statement II explains Statement I

   Both I and II are correct and II explains I. Rare earths in TV and monitor phosphors work because some REEs are phosphorescent / luminescent.

2. B

   Both Statement I and Statement II are correct but Statement II does not explain Statement I

   Both correct but II does not explain I. The phosphor property is exactly why they are in screens.

3. C

   Statement I is correct but Statement II is not correct

   I correct, II not. They do have those optical properties.

4. D

   Statement I is not correct but Statement II is correct

   I not, II correct. They are used in screens.

Summary. Official Set A key is (a). Some rare earths (e.g. europium, terbium, yttrium compounds) are used in display phosphors (I) because they luminesce / phosphoresce (II). II is why I is true.