Which among the following sugars is called as laevulose?

Assertion : Treatment of $D$-glucose with dilute alkali affords an equilibrium mixture consisting of $D$-mannose,$D$-fructose and starting substance $D$-glucose.
Reason : The reaction involves an intermediate in which hybridization of $C_2$ changes from $sp^3$ to $sp^2$.

How do you explain the presence of all the six carbon atoms in glucose in a straight chain?

Given below are two statements:
Statement $I$: The two cyclic forms of $D-(+)-glucose$ ($\alpha$ and $\beta$ anomers differing at $C1$ hydroxyl orientation) are two anomers of $D-(+)-glucose$.
Statement $II$: The open chain forms of $D-glucose$ and $D-fructose$ contain three similar chiral carbons at $C3$,$C4$,and $C5$.
In the light of the above statements,choose the correct answer from the options given below:

Which of the following is a trisaccharide?

The incorrect statement among the following is: