Review the passage:
Marcus has no consideration for the ecosystem rich with
life in his backyard. When he cuts the lawn, he slows for nothing.
As toads, lizards, and insects jump to the sanctuary of bushes to avoid
the deadly mower blades.
You chose the first part, Marcus has no consideration for the ecosystem rich with life in his backyard. This part has a main clause: Marcus is the subject; has is the verb. A fragment will not have a main clause.