Students design a filter for muddy pond water. Notes say: produces 500 mL with no visible mud, uses two coffee filters, costs under $8, tested in one period. Which note is a criterion?

A team designing a model bridge lists: holds 3 kg for 30 seconds, may use 25 straws, may use 1 m tape, has 40 minutes. Which listed item is a criterion?

For a solar oven prototype, notes read: heats 100 mL of water to 50°C, uses cardboard, no glass, fits in a backpack. Which note describes a criterion?

A phone stand for recording experiments must keep the camera steady, fit in a 10 cm drawer, use scrap cardboard, and be built today. Which need is a criterion?

Students improve a cafeteria tray carrier. Their notes include: carry full trays without tipping, mass below 1 kg, cost under $10, use washable plastic. Which note is a criterion?

Students build a stormwater barrier for a sand tray. Their notes: keeps sand in the tray, uses 12 craft sticks, fits a 30 cm tray, built in 20 minutes. Which note is a criterion?

Notes for a classroom doorstop prototype: holds a door open on tile, uses rubber bands, uses cardboard, built in 15 minutes. Which note is the criterion?

A bird feeder should keep seed dry and hang safely. The team can use only one plastic bottle. Which statement is a constraint?

In a plant-watering design, the device must give 50 mL per day and not flood soil. It cannot use electricity over the weekend. Which statement is a constraint?

A toy car ramp should carry a car safely across a 30 cm gap. Builders are given only 2 m of tape. What part of the problem is a constraint?

In a helmet-padding test, success means lowering the force on a falling cup. Each prototype may use at most 50 g of foam. Which statement is a constraint?

A lunch cooler should keep yogurt below 5°C until noon. It must fit inside a 25 cm cubby. Which part states a constraint?

A flood-sensor housing must protect electronics from splashes. The school only allows materials that can be recycled after testing. Which statement is a constraint?

For an egg-drop package, success is an uncracked egg after a 2 m drop. The package mass cannot exceed 100 g. Which statement is a constraint?

A classroom plant dries out each weekend. The solution cannot use electricity and must serve one pot on a windowsill. Which problem statement is most precise?

Wet soccer balls leave puddles in a storage closet after practice. The school has scrap PVC pipe and a tray. Which problem statement is most precise?

An aquarium near a sunny window warms above 26°C. Students may spend $10 and cannot block the front view. Which problem statement is most precise?

During shake tests, books slide off an open classroom shelf. The teacher needs labels visible and the guard removable. Which problem statement is most precise?

Pencils roll off a lab cart when it turns corners. Students have cardboard and tape, and the cart top is 40 cm wide. Which problem statement is most precise?

Leaves fall into an outdoor turtle tub, but the cover must let air and light through. The budget is $15. Which problem statement is most precise?