In Bash, the correct syntax for defining a function is to use the 'function' keyword followed by the function name and curly braces to enclose the commands of the function. To output the sum of two numbers, we can use the 'echo' command and arithmetic expansion with $(($1 + $2)). This allows us to pass two arguments to the function, add them together, and print the result. The other options use incorrect keywords or do not perform the arithmetic operation correctly.
The command sequence uses 'echo' to produce the string '1 2 3 4 5 6', which is then piped into a 'while read' loop. The 'read' command reads into three variables 'a', 'b', and 'c'. Since 'read' splits the input by spaces, 'a' gets '1', 'b' gets '2', and 'c' gets '3'. The 'echo' command in the loop then prints 'result: $c $b $a', which translates to 'result: 3 2 1'. The 'while' loop only runs once because the 'read' command consumes the whole input in one go when it reads into multiple variables and doesn't process remaining input fields separately. Thus, the output is 'result: 3 2 1'.
The command echo $? outputs the exit value of the command executed immediately before echo. If the output is 1, it indicates that the prior command terminated with a non-zero exit value, usually signifying an error or failure.
The missing word in the SQL statement is 'values'. The correct SQL syntax for inserting a new row into a table is 'insert into tablename values (909, 'text');'. The 'values' keyword specifies the data to be inserted into the corresponding columns of the table.