After soaking for one hour in a solution of unknown concentration, a slice of potato appears to be very soft and limp. You can determine that the solution is

Choice A rationale: Only use lower power magnification is incorrect because this does not solve the problem of the dark field of view, but rather avoids it. Using lower power magnification means that you will not be able to see the details of the specimen that you want to observe under the 40x objective lens. Lower power magnification also has a larger field of view and a lower resolution than higher power magnification.

Choice B rationale: Add more immersion oil is incorrect because immersion oil is only used for the highest magnification objective lens, which is the 100x oil immersion objective lens, not the 40x objective lens. Immersion oil is a type of oil that has the same refractive index as glass, which means that it bends light in the same way as glass. Immersion oil is applied between the slide and the lens to reduce the refraction of light and increase the clarity of the image.

Choice C rationale: Adjust the fine adjustment knob is incorrect because the fine adjustment knob is used to fine-tune the focus of the specimen, not the brightness of the field of view. The fine adjustment knob is a small knob that is located on the side of the microscope, next to the coarse adjustment knob. The fine adjustment knob is used to make small changes in the distance between the objective lens and the specimen, which improves the sharpness of the image.

Choice D rationale: Increase the light intensity is correct because the light intensity is the amount of light that reaches the specimen and the objective lens, which affects the brightness of the field of view. The light intensity can be adjusted by using the rheostat, which is a dial that is located on the base of the microscope, next to the light source. The rheostat can increase or decrease the voltage of the light source, which changes the brightness of the light. Increasing the light intensity can make the field of view brighter and easier to see.

Diffusion is the movement of particles from an area of higher concentration to an area of lower concentration across a semi-permeable membrane. Diffusion stops when there is no net movement of particles across the membrane, which means that the rate of diffusion in one direction is equal to the rate of diffusion in the opposite direction.

This does not necessarily mean that there is an equal concentration of particles on both sides of the membrane, but rather that there is a dynamic equilibrium between the two sides. For example, if a semi-permeable membrane separates a solution of 10% sugar and 90% water from a solution of 20% sugar and 80% water, diffusion will occur until the sugar concentration on both sides is 15%.

However, if the membrane only allows water to pass through, diffusion will occur until the water concentration on both sides is equal, which means that the sugar concentration on one side will be higher than the other. Therefore, diffusion does not always result in an equal concentration of particles on both sides of a semi-permeable membrane.