Mrs. Jones was reading a letter at breakfast. Suddenly she looked up
suspiciously at her husband. "Henry," she said, "I've just received
a letter from mother saying she isn't accepting our invitation to
come and stay, as we do not appear to want her. What does she mean
by that? I told you to write and say that she was to come at her own
convenience. You did write, didn't you?" "Er, yes, I did," said the
husband. "But I couldn't spell convenience, so I used risk instead."