SI: One of the many young scientists who chose to throw in their lot with Rutherford was an Oxford physical chemist, Frederick Soddy. S6 : We now know that Gamma rays are a particularly fierce form of X-rays. P : His association with Rutherford lasted only two years, but that was long enough to change the whole face of physics. Q : He was just 23. R : They found that thorium changed into a new element, thorium X, and in the process gave off what was apparently a gas and at the same time a third type of ray, which they named after the Greek letter ‘Gamma’. S : When he teamed up with Rutherford, they investigated thorium which, as Marie Curie had shown, was radioactive. The proper sequence should be
- AP Q S R
- BQ P S R
- CQ P R S
- DQ S R P
Explanation
Q introduces Soddy's youth (just 23), the natural detail after S1 names him. P summarizes the two-year association that changed physics. S describes the joint work: investigating thorium. R gives the discovery: thorium X, the gas, and the third ray named Gamma. S6 closes on Gamma rays being a fierce form of X-rays, which follows R. Hence QPSR, i.e. option B.