Cytosine is not a polymer but rather a nucleobase, one of the four main chemicals that form the fundamental building blocks of DNA and RNA. Along with thymine, adenine, and guanine, cytosine plays a critical role in the encoding of genetic information. DNA and RNA sequences are composed of long chains of nucleotides, which serve as the polymers in this context. Each nucleotide consists of a sugar (deoxyribose in DNA and ribose in RNA), a phosphate group, and a nucleobase (like cytosine). Therefore, while cytosine itself is not a polymer, it is part of the nucleotide unit that combines in sequences to form the polymers DNA and RNA, which store and transmit genetic information.

Substituting black ink with color in a printer involves accessing the printer settings through either the computer’s control panel or the printer's display screen. Look for an option named something like “Print in Grayscale” or “Black Ink Only” and disable it. Then, select a color option, usually found under a “Print Quality” or “Advanced Settings” menu. Some printers and software allow you to choose specific color combinations or to use only one color at a time. Keep in mind, this method is more of a workaround and may not be supported by all printers. The color ink may not replicate the sharpness or depth of true black ink, and it will likely increase the use of your colored inks, potentially raising costs.

PVA glue, or Polyvinyl Acetate, is a type of adhesive commonly used in crafts, woodworking, and construction. It is water-based, making it easy to clean up with water before it dries. Upon drying, PVA glue becomes transparent and forms a strong bond that is flexible yet durable. It is non-toxic, making it safe for use in schools and by children. PVA glue is best used on porous materials, including wood, paper, and fabric. It is not suitable for use on plastics or metals. Variants like white glue, school glue, and wood glue are all based on PVA, each modified for specific applications. Its versatility and safety profile make PVA glue a staple in both professional and hobbyist settings.