Awater molecule is lost when two glucose units come together to form a molecule of lactose. which type of reaction is involved in the formation of the lactose molecule?

When two monosaccharaides e.g. glucose  join together to form a disaccharide,  the resulting bond is known  as glycosidic bond and is formed through a condensation reaction where a water molecule is lost in the process.

The condensation reaction occurs when an alcohol group (OH) from a molecule  reacts with the anomeric carbon of a sugar. The anomeric carbon is the central carbon of a hemiacetal.  The OH group bonded to that carbon is  replaced by the O of the alcohol , and the H of the alcohol is  removed. Together they make water which is then released and lost.

instead of copying and pasting things off of tests or work done on computer which im sure you did, try and read over the question carefully

they have identical fossils of organisms that have evolved over time.

both have animal fossils preserved in them due to weathering and erosion.

they contain different fossils because life on earth has changed through time.

the fossils in them were formed on the surface of earth due to exposure to sunlight.