Pls help guys I rlly don't know what's the right answer

What best discribes the relationship between wavelength and frequency in a electromagnetic wave

Explain in detail of the four major scientific developments that spurred the formulation of the plate tectonics theory

Achemist who studies water samples did a demonstration of how to test for lead in water. she added a clear solution of potassium iodide to a clear solution of lead nitrate. then a yellow swirling solid formed in the liquid. what is most likely true about the yellow solid?