Answer:
C. Select a number from {1, 2, 3, 4, 5, 6} and a vowel.
Step-by-step explanation:
Let's start this with a simple example: how many messages are possible using one number from {7, 9} and one letter from {a, b}. It will be 4 as 7a, 7b, 9a and 9b. This result can also come by multiplying the number of digits used and number of alphabets used - here number of digits are 2 (they are 7 and 9) and number of alphabets used are 2 (they are 'a' and 'b'). So 2 × 2 = 4.
[NOTE : In this question 7a and a7 are same]
Maximum number of options consists of vowels as letters so we will first find the number of digits needed if vowels are used as letters.
The number of vowels are 5 (they are 'a', 'e', 'i', 'o', 'u').
The number of possible precodes needed = 30
Let the number of digits needed be 'n'.
Then n × 5 = 30
∴ n = 6
Therefore the number of digits needed is 6 which is there in option C. The digits are {1, 2, 3, 4, 5, 6}
Therefore option C is the answer.
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Step-by-step explanation:
