This letter, this pencil., that man, that woman, this desk, this office, this house, this cable, this city, that class надо во множественном числе.

Указательное местоимение "this" (это, этот) во множественном числе имеет форму "these" (это, эти). Указательное местоимение "that" (тот) преобразуетс в "those" (те).

This letter - these letters, this pencil - these pencils, that man - those men, that woman - those women, this desk - these desks, this office - these offices, this house - these houses, this cable - these cables, this city - these cities, that class - those classes.