Silent-Letter Words

Spelling is a difficult skill for many students.  Many words in English are not spelled the way they sound.  Further, even when rules apply,  the number of rules governing correct governing correct spelling is very large.   
One of the vexing problems when attempting to spell words is that some words contain silent letters.  Having your students become familiar with silent-letter words can improve their spelling.
Each of the following words contains a silent letter.  Have your students identify the silent letter in each word.
muscle (c)
soar (a)
castle (t)
subtle (b)
raspberry (p)
could (l)
wrong (w)
sign (g)
Have your student identify other examples of silent-letter words.