$56.$ The primary purpose of $\_\_\_$ and $\_\_\_$ in the petrochemical industry is to serve as precursors for various chemicals such as methanol and ammonia. $($a$)$ Synthesis gas, hydrogen $($b$)$ Ethylene, butylene $($c$)$ Acetylene, propylene $($d$)$ Methane, propane

$57.$ The process of $\_\_\_$ involves the conversion of methane and steam into synthesis gas, while $\_\_\_$ involves the conversion of hydrocarbons into smaller molecules. $($a$)$ Steam reforming, catalytic cracking $($b$)$ Hydrocracking, steam reforming $($c$)$ Catalytic reforming, steam cracking $($d$)$ Steam cracking, hydrocracking