In the process $BCl_3 + PH_3 \to BCl_3:PH_3$,the Lewis acid is

The number of $S-S$,$S-O-S$,and $O-H$ linkages in a molecule of pyrosulphurous acid $(H_2S_2O_5)$ are respectively

Which of the following statements is incorrect?

Which one of the following statements is correct?

Which of the following is a Lewis acid?

For the following species,determine whether the octet rule is obeyed or not obeyed. Provide the reason for each:
$(1) BeF_4^{2-}$
$(2) BF_3$
$(3) CO_2$
$(4) NO$
$(5) NH_3$