# Find the VMs with questions
$vms = get-view -viewtype virtualMachine | ?{ $_.runtime.question }

# Answer the questions
foreach ($vm in $vms) {
  Get-VM $vm.name | Get-VMQuestion | Set-VMQuestion -DefaultOption
}

# You could also do this, but Get-VMQuestion seems to be *very* slow:
$questions = Get-VMQuestion
foreach ($question in $questions) {
  Set-VMQuestion -VMQuestion $question -DefaultOption
}