[Answer] If the names of NASA's space shuttles are listed alphabetically, how many missions were flown by the fourth one on the list?

Step 1 : Introduction to the question "If the names of NASA's space shuttles are listed alphabetically, how many missions were flown by the fourth one on the list?"

...Hint :D

[Ans] Based on their chemical symbols, which of these elements comes first alphabetically?

Step 1 : Introduction to the question "Based on their chemical symbols, which of these elements comes first alphabetically?"

Many symbols for chemical elements stem from classical Latin and Greek vocabulary. For some elements, this is because the material was known in ancient times, while for others, the name is a more recent invention. For example, the Latin name for gold is aurum. Thus, the chemical symbol for gold is Au. The symbol for lead is Pb (plumbum in Latin); Hg is the symbol for mercury (hydrargyrum in Greek). Some symbols come from other sources, like W for tungsten (Wolfram in German) which was not known in Roman times.

[Answer] Based on their chemical symbols, which of these elements comes first alphabetically?

Step 1 : Introduction to the question "Based on their chemical symbols, which of these elements comes first alphabetically?"

...Many symbols for chemical elements stem from classical Latin and Greek vocabulary. For some elements, this is because the material was known in ancient times, while for others, the name is a more recent invention. For example, the Latin name for gold is aurum. Thus, the chemical symbol for gold is Au. The symbol for lead is Pb (plumbum in Latin); Hg is the symbol for mercury (hydrargyrum in Greek). Some symbols come from other sources, like W for tungsten (Wolfram in German) which was not known in Roman times.