Given that,
\(k\) divides \(m+2n\) and \(3m+4n\).
Since \(k\) divides \((m+2n)\)
\(⇒ k\) will also divide \(3(m+2n)\)
\(⇒ k \) divides \(3m+6n\)
Similarly,
\(k\) divides \(3m+4n\).
We know that, if two numbers \(a\) and \(b\) both are divisible by \(c\), then their \((a-b)\) is also divisible by \(c\).
By the same phenomenon,
\([(3m+6n)-(3m+4n)]\) is divisible by \(k\).
So, \(2n\) is also divisible by \(k\).
Now, \((m+2n)\) is divisible by \(k\),
\(⇒ 2(m+2n)\) is also divisible by \(k\).
\(⇒ 2m+4n\) is also divisible by k.
So, \([(3m+4n)-(2m+4n)] = m\) is also divisible by \(k\).
Therefore, \(m\) and \(2n\) are also divisible by \(k\).
So, the correct option is (D): m and \(2n\)