What types of microbes live in the intestines?
diverse species of bacteria, archaea, and fungi, especially bacteroides and firmicutes bacteria
a narrow range of bacteria, especially firmicutes
a narrow range of bacteria and fungi, especially bacteroides
archaea and fungi only

Option A,  

Diverse species of bacteria, archaea, and fungi, especially Bacteroides and Firmicutes bacteria

Explanation:

The environment with in the small intestine is milder than the large intestine, thus it can sustain large number of bacteria’s including the  lactobacilli, diptheroids and certain fungi such as candida.  

On the other hand a large intestine consists of a diverse set of bacteria’s such as bacteriodeted, Firmicutes ,  algaes like Methanognic archaea and fungi.  

Hence, option A is correct