"Which of the following data types are incorrect" The answers are "b" and "d": VARCHAR fields can only hold 255 characters, and LONGINT doesn't exist in MySQL, you should use BIGINT.
"Suggest the ideal data type for the following fields". For "First name" you should have answered with a VARCHAR of sorts, for "Age" a small INT field, for "Height" another small INT field (and convert things like feet and inches into plain old inches), and for "Life story" I think TEXT should suffice.
"When are LOW_PRIORITY-marked writes executed" The answer is "c": when no more reads remain.
"Temporary tables are automatically deleted when your scripts ends: true or false" True.
"Which of the following statements are true about indexes" The correct answer is "e".
"You can emulate subselects using multiple individual queries: true or false" True, but hard work!
"Unbuffered queries allow you to start reading in the result of a query before the query has been finished: true or false" True, but don't try to count the number of rows until the query has finished executing.
"What is SQLite's key advantage over MySQL and other DBMSs" It doesn't use a client/server architecture, so is easier to install and distribute.
"Using PEAR::DB is usually as fast if not faster than standard database calls: true or false" False: PEAR::DB is pretty slow, actually.