question: Complete the next sentence:

How to clean grout with toilet cleaner
Look for a toilet cleaner that contains sodium hydroxide.
Many toilet cleaners contain sodium hydroxide and sodium hypochlorite. These two ingredients help to remove stains and grime on porcelain or tile surfaces as well as grout.

answer: Though they can be toxic in large amounts, they do work to effectively clean grout. You may look for common brands of toilet cleaner at your local hardware store or in the cleaning aisle at your grocery store.

question: Complete the next sentence:

How to hit a tweener in tennis
Know when to use it.
Hitting a tweener should only be used in certain circumstances. The only time you should consider using the shot is when you have come to the net, but your opponent hits a lob over your head.

answer: When running back, you may realize you have no chance of running past the ball, turning around, and hitting it normally, in which case you plan the tweener. If you do have a chance to run past the ball and hit it as a groundstroke, you certainly should do so.

question: Complete the next sentence:

How to relax on an airplane
Choose your preferred airline.
Make sure that the airline's seats have a seat pitch just right for you and that there is some forms of entertainment provided for you (especially for long flights). If there is no entertainment for you, bring your own forms of entertainment such as books or a tablet to keep you awake.

answer:
Make sure that the airline of your choice does not have too many stopovers. Also ensure that the duration of the stopover is no longer than 5 hours.