This is a complex sentence. The main clause is the polar bear sometimes reaches temperate latitudes; the subordinate clause is which lives in the Arctic regions when it is at home, which is complex, since it contains the adverbial clause when it is at home, modifying the verb lives.
This is a complex sentence. The main clause is he says; the subordinate clause is that the polar bear lives in the Arctic regions. The subject of the sentence is he, the complete predicate is says that the polar bear lives in the Arctic regions. The simple predicate is says, which is completed by its direct object, the noun clause that ... regions, introduced by the conjunction that. [Then analyze the subordinate clause.]
5. That the polar bear sometimes reaches temperate latitudes is a familiar fact.
This is a complex sentence. The main clause (is a familiar fact) appears as a predicate only, since the subordinate clause (that the polar bear sometimes reaches temperate latitudes) is a noun clause used as the complete subject of the sentence. The simple predicate is is, which is completed by the predicate nominative fact. This complement is modified by the adjectives a and familiar. The subordinate clause, which is used as the complete subject, is introduced by the conjunction that. [Then analyze this clause.]
COMPOUND COMPLEX SENTENCES
461. In analyzing a compound complex sentence, we first divide it into the independent clauses (simple or complex) of which it consists, and then analyze each of these as if it were a sentence by itself.
See the examples in [§§ 456], [457].