For odd no of tosses
We have
1, 3 ,5,7.........
Q
(1/2)1+ (1/2)3 +(1/2)5 +(1/2)7 ..........
As we can see this is decreasing gp series
So sum ut upto infinity.
S=a/(1-r)
a is first term of the series
r is common. Ratio.
So answer is 0.50/0.75
= 2/3
(c) option