Final answer:
The tissue with many fibers tightly packed in a parallel arrangement observed by the histologist is dense regular fibrous connective tissue, commonly found in tendons and ligaments.
Step-by-step explanation:
When a histologist examines a tissue slide and observes many fibers tightly packed together in a parallel arrangement with a few cells squeezed between the fibers, the tissue in question is likely dense regular fibrous connective tissue. This type of tissue has collagenous fibers arranged in parallel bundles and is typically found in structures such as tendons and ligaments, which require high tensile strength in one direction.
Other options like areolar connective tissue, adipose connective tissue, and dense irregular connective tissue have different characteristics. Areolar connective tissue has a loose arrangement, adipose is specialized for fat storage, and dense irregular connective tissue has fibers that crisscross and form a mesh, providing strength in multiple directions.