Which of the following changes transformed the union certification process established by the National Labor Relations Act into a lengthy procedure? $($Check all

that apply.$)$

The Supreme Court required employers and unions to follow laboratory conditions standard during the election process.

The Supreme Court and Section $8($c$)$ of the Taft$-$Hartley Act explicitly permitted $($noncoercive$)$ employer participation in the certification process.

The Supreme Court let employers to demand a secret ballot election, even if majority status confirmed by signed authorization cards is not in doubt.

The Taft$-$Hartley Act required unions to establish majority support of employees before filing a petition for representation election.