Final answer:
Biotrophic fungi use direct penetration to enter cells via structures called haustoria, extracting nutrients from living host cells.
Step-by-step explanation:
The type of fungi pathogen that uses direct penetration to enter cells is biotrophic fungi. Biotrophic fungi, like the powdery mildews and rusts, produce specialized structures known as haustoria which penetrate plant cell walls and allow the fungi to access and extract nutrients from the living cells of their hosts. These fungi are considered obligate parasites because they can only derive nutrients from living cells.