16 checkpoints
... that California maintains 16 checkpoints along its borders with Oregon, Nevada, and Arizona to help protect against an invasion by exotic lifeforms?
... that <a href="./California" id="mwAec" rel="mw:WikiLink" title="California">California</a> maintains <b id="mwAeg"><a href="./California_Border_Protection_Stations" id="mwAek" rel="mw:WikiLink" title="California Border Protection Stations">16<span id="mwAeo" typeof="mw:Entity"> </span>checkpoints</a></b> along its borders with <a href="./Oregon" id="mwAes" rel="mw:WikiLink" title="Oregon">Oregon</a>, <a href="./Nevada" id="mwAew" rel="mw:WikiLink" title="Nevada">Nevada</a>, and <a href="./Arizona" id="mwAe0" rel="mw:WikiLink" title="Arizona">Arizona</a> to help protect against an invasion by exotic <a href="./Outline_of_life_forms" id="mwAe4" rel="mw:WikiLink" title="Outline of life forms">lifeforms</a>?