Which of the following reactions will occur spontaneously as written?
a) 3fe2+ (aq) + cr3+ (aq) → cr (s) + 3fe3+ (aq)
b) 2cr3+ (aq) + 3sn2+ (aq) → 3sn4+ (aq) + 2cr (s)
c) sn4+ (aq) + fe2+ (s) → sn2+ (aq) + fe (s)
d) sn2+ (aq) + fe2+ (s) → sn4+ (aq) + fe3+ (aq)
e) 2cr (s) + 3fe2+ (s) → 3fe (s) + 2cr3+ (aq)

organisms are more likely to be more preserved in mud than sand because mud is moist and wet, while sand is very dry.

answer is: nuclear fusion produces elements that are heavier than helium.

nuclei combine to form a heavier nucleus, releasing energy.  

for example, fusion of hydrogen atoms at the sun.  

this fusion nuclear reaction is in the inner core of the sun and hydrogen (atomic number 1) is conveted into helium (atomic number 2).  

the inner core is the central region of the sun and all solar energy is produced in the core by nuclear fusion.