Answer:
C , T , I , O , S , H , K
Step-by-step explanation:
A 1-fold reflectional symmety means that if the letter is folded in the middle (either horizontally or vertically) then both sides will be identical and match up perfectly. From the words provided the letters that have this symmetry are the following.
From "RAINY" = I
From "ACTION" = C , T , I , O
From "SHARK" = S , H , K
Each of these letters can be folded once and have both parts identical to one another.