Question

fields ________. (choose all that apply)
are always invisible
can be measured
cannot be measured
can have motion
never have motion

Explanation:

• For "are always invisible": Fields like electric, magnetic, or gravitational fields are invisible to the naked eye, so this applies.
• For "can be measured": We can measure properties of fields (e.g., electric field strength, magnetic field flux), so this applies.
• For "cannot be measured": This is incorrect as we can measure field - related quantities.
• For "can have motion": Fields can change over time (e.g., a changing magnetic field in electromagnetic induction), so they can have a form of motion (change in their state/configuration over time).
• For "never have motion": This is incorrect as fields can change (which is a form of motion in terms of their temporal variation).

Answer:

• are always invisible
• can be measured
• can have motion