Final answer:
The correct option is A. Desmosomes are the protein bonds in the stratum spinosum that form strong 'spot welds' between adjacent epithelial cells, giving tissue its strength.
Step-by-step explanation:
The protein bonds that develop in the stratum spinosum, creating junctions between cells, are called desmosomes. Desmosomes act like spot welds between adjacent epithelial cells, providing strength and rigidity to tissues.
They are composed of proteins such as cadherins, which span between cells, and intermediate filaments that anchor these structures, thereby creating a very strong 'spot weld' between cells.