A [s] sound follows words that end with a voiceless sound like [k], [p], [t]: for example after the simple present forms meets, asks, starts, likes, hates and the plural forms plates, books, drinks, lips. Listen to the words.
A [z] sound follows words that end with a voiced sound like [b], [d], [l], [m], [n], [v], [ r] or a vowel-sound (a, e, i, o, u, y, ie, …): for example after the simple present forms moves, goes, is, tells, drives and the plural forms planes, names, phones, neighbours, opportunities, boys. Listen to the words.
A [ɪz] sound follows words that end with so-called sibilant sounds like [s], [z], [ʃ], [tʃ], [ɖɮ], [x]: for example after the simple present form changes, watches, fixes and the plural forms boxes, glasses, houses and the noun bridges Listen to the words.