This question asks us to find the number of meaningful English words that can be formed using specific letters from the word "CONSISTENCY". We need to use the 3rd, 4th, 7th, and 8th letters only once for each word.

Identifying Key Letters from CONSISTENCY

First, let's identify the letters at the specified positions in the word "CONSISTENCY". The word has 11 letters.

Word: C O N S I S T E N C Y

Positions: 1 2 3 4 5 6 7 8 9 10 11

• The 3rd letter is N.
• The 4th letter is S.
• The 7th letter is T.
• The 8th letter is E.

So, the letters we have to work with are N, S, T, E.

Forming Meaningful English Words

The task is to form meaningful English words using these four letters (N, S, T, E), using each letter exactly once in each word. This means we are looking for 4-letter arrangements (permutations) of these letters that form valid words.

The total number of possible arrangements (permutations) of these 4 distinct letters is calculated using the factorial formula:

In this case, $n=4$ (number of letters available) and $k=4$ (length of the word to be formed). So, the total number of permutations is:

Now, let's check which of these 24 arrangements are meaningful English words:

• NEST: This is a meaningful English word (a bird's home).
• NETS: This is a meaningful English word (plural of net).
• SENT: This is a meaningful English word (past tense of send).
• TENS: This is a meaningful English word (plural of ten).
• STEN: This is a less common word, referring to a type of firearm or a surname, but it is recognized in some dictionaries.
• ENTS: This can refer to mythical tree-like creatures or sometimes a shorthand, but it's less common as a standard dictionary word compared to the others.

Considering the most common and widely accepted English words formed from these letters, we find four primary words:

1. NEST
2. NETS
3. SENT
4. TENS

Therefore, there are 4 meaningful English words that can be formed using the letters N, S, T, E exactly once.

Matching the Count to the Options

The number of words found is 4. Comparing this to the given options:

• One
• Two
• Three
• Four
• More than four

The count of 4 matches the option "Four".