On what basis are the three types of lichens classified?

$A$ finite ladder is constructed by connecting several sections of $2\,\mu F$ and $4\,\mu F$ capacitor combinations as shown in the figure. It is terminated by a capacitor of capacitance $C$. What value should be chosen for $C$ such that the equivalent capacitance of the ladder between the points $A$ and $B$ becomes independent of the number of sections in between? (Answer in $\mu F$)

$A$ healthy person eats the following diet: $5 \ gm$ raw sugar,$4 \ gm$ albumin,$10 \ gm$ pure buffalo ghee adulterated with $2 \ gm$ vegetable ghee (hydrogenated vegetable oil) and $5 \ gm$ lignin. How many calories is he likely to get?

In a book of $500$ pages,it is found that there are $250$ typing errors. Assume that Poisson law holds for the number of errors per page. Then,the probability that a random sample of $2$ pages will contain no error,is :

Which of the following pairs of straight lines intersect at right angles?

An object is attached to the bottom of a light vertical spring and set vibrating. The maximum speed of the object is $15 \, cm/s$ and the period is $628 \, ms$. The amplitude of the motion in centimeters is