Arun
Last Activity: 7 Years ago
We have
|a x r|² + |a.r|² = |a|² |r|²
| j|² + (a. r)² = |a|² |r|²
(a. r) = + -

(|a|² |r|² - 1)
This shows that (a. r) depends on |r | on a given a.
Hence (a.r) is any arbitrary scalar.
Option D is correct.
Regards
Arun(askIITians forum expert)