Which of the following are true regarding hydroboration of alkene `?(` More than one correct statements . `)`
A. Reaction proceeds through ionic intermediat and syn`-`addition take place.
B. Reaction proceeds through cyclic intermediate transition state and syn`-` addition takes place.
C. Reagent diborane in ether `(THF)` exists as `:`
.
D. Reagent exists in `THF` as borane `-THF` complex.
