Into how many subclasses is the class $Dicotyledonae$ divided?

$A$ binary sequence is an array of $0$'s and $1$'s. The number of $n$-digit binary sequences which contain an even number of $0$'s is

What is meant by $Tin \ Cry$?

In a transistor,if $\frac{I_C}{I_E} = \alpha$ and $\frac{I_C}{I_B} = \beta$. If $\alpha$ varies between $\frac{20}{21}$ and $\frac{100}{101}$,then the value of $\beta$ lies between:

Which of the following statements is true?

When a train stops suddenly,passengers in the running train feel an instant jerk in the forward direction because