  Discoveries of tetraquarks not only enrich the hadronic spectrum but also
provide more platforms to understand quantum chromodynamics. We study the
production processes of hidden-charm and open-charm tetraquarks in $B$ decays
by analyzing their topological amplitudes. Relations between different channels
are found, which confront tests by experiments to probe the nature of the
tetraquarks. Furthermore, promising channels to find more tetraquarks are
proposed.
