Ssample of thorium-234 has a half life of 25 days. will all the thorium undergo radioactive decay in 50 days?

25% thorium will left after 50 days.

Explanation:

Half life:

A nuclear half is the time period of radioactive material in which its amount remain halved.

In given question it is stated that the half life thorium-234 is 25 days. Which means after passing the 25 days the amount of thorium must be halved of original amount.

For example,

If the original concentration was 100%, than after 25 days it will be 50%.

After 50 days amount of thorium left:

Number of half life = T (elapsed) / T half life

Number of half life = 50/25

Number of half life =  2

At first half life amount of thorium left = 100/2 = 50

After second half life amount of thorium left = 50/2 = 25

Total amount decayed = 50+25 = 75

Amount left after 50 days = 100-75 = 25

25% thorium will left after 50 days.

it is b that is the answer.