Always add acid to water. You should mix solutions slowly because you run the risk of solutions spilling, which may ruin your reaction entirely. Rapid mixing can also lead to inadvertently speeding up reactions and releasing energy or heat in a dangerous manner. During dilution of acids with, water heat is released; if a small amount of water is added to a concentrated acid it has the possibility of bubbling over the counter and onto you. 

During the distillation process, the combined substances are heated until the first one boils. The substance that boils and becomes a gas is then separated from the still liquid or solid substance via condensation into a separate container. Filtration involves separating substances in solid and liquid phases through a filter paper, and is often facilitated by a vacuum. Dehydration and hydration are types of reactions where water is a product, and a reactant, respectively. Fermentation is a biochemical process that occurs under anaerobic conditions. Some organisms produce lactic acid as a byproduct of fermentation, (humans), others produce ethanol (yeast). 

When measuring any liquid in the lab, a volumetric pipet or flask is always going to be the most accurate. This makes the 9mL volumetric pipet the best choice.

There is no such thing as a 9mL watch glass. Though a 10mL syringe and graduated cylinder would be quite accurate, the 9mL volumetric pipet is more accurate, and remember the question asked for the best out of the answer choices. A beaker is very inaccurate and should only be used to transfer solutions, not to measure them.  

In a titration, you should use a buret to administer the  solution into the  solution. A buret gives you the most accuracy in running the titration as you can dispense the solution drops at a time. The buret will also allow you to accurately determine the volume of  needed to complete the titration. A watch glass and spatula would be inappropriate for this situation because you are dealing with liquids. Pouring from a graduate cylinder would not be accurate enough and the titration results would be subject to lots of error. A volumetric pipet will not allow you to keep track of the volume needed to complete the titration.

In order for an accurate reading of a graduated cylinder, hold the graduated cylinder at eye level then make sure the bottom of the meniscus is at the desired volume. Having the graduated cylinder slightly below eye level will result in readings that are higher than they are supposed to be. Having the graduated cylinder slightly above eye level will result in readings that are lower than they are supposed to be. Never place your head on the same level as the table to read a graduated cylinder. If the graduated cylinder tips over for any reason, you will splash the solution held within on your face.

A volumetric pipette is made to dispense a specific amount of liquid very accurately. The Mohr pipette, beaker, and graduate cylinder will not measure a specific amount of liquid as accurately as the volumetric pipette.

Potassium hydrogen phthalate is a solid at room temperature, so we can use a balance and a weigh boat or weigh paper. When measuring precise amounts of chemicals, an analytical balance will be able to provide the most accurate reading of mass. 

When you need to heat anything up to high temperatures, you must use a crucible. Glassware is not able to withstand as much heat as a crucible.

A beaker is the best choice for mixing these two solutions. Graduated cylinders, burets, and pipets are all used to measure specific amounts of solution. Also, stirbars can be easily added to beakers to facilitate the reaction.

A spectrophotometer should be used because it is used to measure absorbance at specific wavelengths. An analytical balance is used for measuring mass. Chromatography paper is used to separate different pigments found in a chemical. Litmus paper is used to determine the pH of a substance.