thr-thread, throat, through
thread
str- strange, street, struggle
strange or struggle
str- strap, stray, strip
strap
scr- scrap, screw, scrub
screw
thr- three, threw, throb
throb
spr-spray, spree, sprig
spray
spl-splash, splendid, splinter
splash
spl- splat, splay, split
splat
spr-spread, spring, sprinkle
spring
shr-shriek, shrimp, shrivel
shrimp
scr-scrape, scrap, screen
screen
shr- shred, shrub, shrug
shred
scr-scratch, scream, scribble
scribble