Facts

Letters A, B, C and D do not appear anywhere in the spellings of 1 to 99
Letter D comes for the first time in Hundred

Letters A, B and C do not appear anywhere in the spellings of 1 to 999
Letter A comes for the first time in Thousand

Letters B and C do not appear anywhere in the spellings of 1 to 999,999,999
Letter B comes for the first time in Billion

And

Letter C does not appear anywhere in in the spellings of entire English Counting

Morning Tea