Answer:
It lies in in the <u>visible</u><u> </u><u>region</u><u>.</u>
Frequency: <u>is</u><u> </u><u>7</u><u>.</u><u>4</u><u>0</u><u>7</u><u> </u><u>×</u><u> </u><u>1</u><u>0</u><u>^</u><u>-</u><u>1</u><u>4</u><u> </u><u>Hz</u>

Explanation:
V is speed of light.
f is frequency
lambda is the wavelength
I’m not sure if there was important information in the question before this one, but the answer based on the info I have is B.
The density of water is 1kg/L. Since the density of the block is less, it will float.
Cells are too small to see with the naked eye.
It's pretty straight forward, use the cross-out method.
1) Microscopes MAGNIFY images, they don't color the cells. In fact, scientists have to use these chemicals to "stain" or color the cells to see them more easily through microscopes.
2) If the lenses of a microscope reduced the image of an organism to the size of a cell, you'd be seeing a very tiny human through your microscope, instead of actual cells.
3) Microscopes don't "trap" anything. In fact, scientists use plates or slides under microscopes to contain what they're studying.