a(n) is a high energy electron released from a nucleus during radioactive decay.
alpha
gamma
positron
beta

beta

Explanation:

A beta particle (symbol β) is a high-speed and high-energy electron which is emitted by radioactive decay of the atomic nucleus during process of the beta decay.

Strontium-90 is material which is most commonly used to produce the beta particles.

Beta particles are used to treat conditions such as eye as well as bone cancer.

c is having 4 valence electrons and is bonded to three hydrogens and one sulphur atom, therefore, the number of bond pair is equal to four. as all the valence electrons are used in forming the bonds so, there is no lone pair left on carbon.

s is having 6 valence electrons and is bonded to one other sulfur atom and one carbon atom, therefore, the number of bond pair is equal to 2. as only two valence electrons are used in forming the bonds so, four electrons are left. therefore, two lone pairs are present on s.

a). in this case, dh> 0 and sd> 0. if t becomes larger, the term "-tds" will become more negative. at some point, it is possible that -dts will be more negative than the dh is positive, and the reaction will become spontaneous. this is probably the correct answer, but you should look at all of the other possibilities and make sure of that.