Correct Answer - Option 3 :

\(\frac{1}{2}\)
__Concept:__

Probability of an event happening = \(\frac{{{\rm{Number\;of\;ways\;it\;can\;happen}}}}{{{\rm{Total\;number\;of\;outcomes}}}}\)NumberofwaysitcanhappenTotalnumberofoutcomesNumberofwaysitcanhappenTotalnumberofoutcomes

__Calculation:__

A coin is tossed 2 times

Sample Space = {(H,H) , (H,T) , (T,H) , (T,T) }

∴ Total no of Outcomes = 4

Taking head and tail

Thus, Favourable outcomes are = {(H, T), (T, H)} = 2

∴ Probability of getting head and tail alternately = 2/4 = 1/2