Which of the following expressions is correct?

The RMS velocities of two gases at the same temperature are u_1 and u_2 their masses are m_1 and m_2 respectively. Which of the following expression is correct?

which of the following expression is correct?

Which of the following expression is correct?

Which of the following expression is correct?

which of the following expression is correct?

In an ideal rock salt structure (edge length a) which of the following expression is correct?