Five molecules have speeds of 2.8, 3.2, 5.8, 7.3, and 7.4 m/s. their root-mean-square speed is closest to

The complete question in the attached figure

we know that

the root mean square speed, is the square root of the average (mean) of all of the square of the speeds of individual particles in a gas.

step 1
find the  square of the speeds of individual particles
2.8²----> 7.84
3.2²---->10.24
5.8²----> 33.64
7.3²----> 53.29
7.4²---> 54.76
average=[7.84+10.24+33.64+53.29+54.76]/5-----> 159.77/5----> 31.954

step 2
find the square root of the average
√31.954=5.65

therefore

the answer is
the option b) 5.7 m/s