Easy, ‘a’.

 
Sight Words… Reading and Spelling..Try more words…

a…

Easy…
…..am .NSF2+ +Email Level K1.
…..an .NSF2+ +Email Level K1.
…..and .NSF2+ +Email Level K1.
…..ant .NSF2+Wk Sht + WD SCH +Email/FORM Level K1.
…..as .NSF2+ +Email Level K1.
…..act .NSF2+ +Email/FORM Level K1, 2, 3
…..add
…..at

A bit harder (maybe)…
…..able .NSF2+Wk Sht + WD SCH +Email/FORM Level 2, 3.

Try more words…