need help filling in these blanks:

First blank either "1" or "2"

second blank either "back-side attack" or "a carbocation intermediate"

third blank either "water" or "hydroxide"

4th blank either "tertiary," "secondary," or "primary"

5th blank either "nucleophilic attack," "loss of a leaving group," "protonation of the diol," or "deprotonation of the diol"

Tetrahydrofuran (THF) can be formed by treating 1,4-butanediol with sulfuric acid. Propose a mechanism for this transformation. OH H2SO4 HO 1,4-Butanediol Tetrahydrofuran (THF) 13.31 This substitution reaction is expected to be similar to an SN mechanism, involving because the leaving group is on a carbon that is V The first step of the mechanism is