Answer:
Complex System
Explanation:
Given that, a descriptive scientific investigation is one of the three main types of investigation which formulates and quantify the natural phenomenon. This natural phenomenon oftentimes involves Complex System, such as microscopic organisms, thereby, scientists often make observations to understand the interacting parts of this COMPLEX SYSTEM
Hence, the right answer is a COMPLEX SYSTEM
Suspension is defined as the heterogeneous mixture in which solute particles suspended throughout the bulk of the particles. The particle size is more than 100 nm. In suspension, particles don't pass through filter paper. Sand in water is an example of suspension.
Colloid is defined as a mixture (heterogeneous and homogeneous) in which one substance of dispersed insoluble particles get suspended throughout other substance. The particle size is 1 to 100 nm. In colloid, particles are small, thus pass through filter paper. The particles of air which is dispersed in solid stone is an example colloid.
Emulsion is a mixture of two or more substance which are immiscible in nature. It is a part of colloid. Milk is an example of emulsion.
Solution is a homogeneous mixture with clear or transparent appearance. The particle size in solution is 
i.e. molecule in size. There is no effect of light occurs in the solution and solution can't filtered but can separated by the physical technique i.e. distillation.
Answer:
Bacteria can evolve quickly because they reproduce at a fast rate.
Explanation:
Bacteria can evolve quickly because they reproduce at a fast rate. Mutations in the DNA of bacteria can produce new characteristics. A random mutation might cause some bacteria to become resistant to certain antibiotics, such as penicillin.
When two element combine to form more than one compound i hope this helps you with work have a nice day :)
The best option is melting point
