Please choose the correct ending to complete the given sentence: Health: [header] How to remove harmful chemicals from your home using houseplants [title] Determine how many houseplants you need for cleaner air. [step] Most of the research done on the air filtering effects of houseplants has been conducted as part of nasa's clean air study program. Nasa's recommendation is growing 1 houseplant for every 100 square feet (9 square meters) of your home's floor area.

Ending1: Ideally, these plants should be spread around your home as much as possible. [title] Reduce the emission of harmful compounds as much as possible. Ending2: [substeps] A home with a good air filter is much better. There is enough pollution in the home for fewer air filters. Ending3: The ideal household for use near water is at least 75 gallons (79 l). Finding the right demographic is the simplest equation for removing house plants from your home. Ending4: [substeps] Never divide the cost of a household air filter between houseplants. For example, finding 3 houseplants equals 1 gallon (3.8 l) of water over 100 square meters of floor area.

Answer format: ending1/ending2/ending3/ending4