Some words have letters that we don't pronounce (say out loud) when we read them. These are called silent letters.
The word lamb has a silent 'b'.
The word calf has a silent 'l'.
We just have to learn which words have silent letters, but it might be helpful to remember that in many words with a silent 'b' the letter 'm' comes just before.
Read these words carefully as you will need to spell them correctly in this worksheet. They all have either a silent 'b' or a silent 'l' in them.