The gas used for filling weather balloons is-

The major constituent of air is

One of the constituents of tear gas is

The most reactive among the halogens is-

The fuel that is used in modern submarines is -

The noble gas used in radiotherapy is

The element used in the manufacture  of safety matches is —

Formation of ozone hole is maximum over

Milk tastes sour when kept in the open for sometimes due to the formation of-

Which one amongst the following is  not a Green House gas?