Sometimes nouns take weird forms and can fool us into thinking they're plural when they're really singular and vice-versa. Consult the section on the Plural Forms of Nouns and the section on Collective Nouns for additional help. My glasses were on the bed. My pants were torn. A pair of plaid trousers is in the closet.
Some words end in -s and appear to be plural but are really singular and require singular verbs.
The news from the front is bad. Measles is a dangerous disease for pregnant women. On the other hand, some words ending in -s refer to a single thing but are nonetheless plural and require a plural verb. My assets were wiped out in the depression. The average worker's earnings have gone up dramatically.