pr --press,pride, price, print, proof

tr --truck,track, true, train, tree

带有s的字母组合

sc --scale,scar, score, scare, scuff

sk --skate,skip, skill, skull, skin

sm --smoke,smile, smog, smell, smear

sn --snake,snap, snore, snow, snug

sp --spoon,spin, spot, spell, sport

st --stop,stack, stay, step, still

sw --swim,swell, swing, sweet, swift

tw --twig,tweet, twist, twin, twine

   三字母组合