A certain unit needs to select personnel to participate in the counterpart poverty alleviation work. Known: If Xiao Li does not participate, then Xiao Ma participates; if Xiao Ma does not participate, then Xiao Li does not participate; either Xiao Ma participates, or Xiao Li participates. Among the following items, the requirements are:. ['Pony participates in counterpart poverty alleviation.', 'Xiao Li participates in poverty alleviation.', 'Xiao Ma and Xiao Li are participating in counterpart poverty alleviation.', 'Xiao Ma and Xiao Li are not participating in counterpart poverty alleviation.']