It is often difficult to know how to spell endings of words when they sound the same. All these words end in either -ible or -able. If you have difficulty remembering one of them, pronounce it to yourself with the "a" or the "i" emphasised.

poss:
prob:
valu:
desir:
terr:
soci:
flex:
respons:
depend:
miser:
incred:
sens:
irrit:
convert: