Which is the strongest acid (`pK_(a)` value is given)?

Which halogen acid is the strongest acid ?

Which of the following is relatively weak acid ? ( pK_(a) values are given in brackets)

Which acid has lowest value of pK_(a) ?

Which of the following is strongest acid?

Which of the following indicators is best suited in the titration of a weak acid versus a strong base? (PK_(10 ) values are given in bracket)