During which phase of mitosis do the nuclear envelope and nucleolus completely disappear?

$A$ body $A$ starts from rest with an acceleration $a_1$. After $2 \ s$,another body $B$ starts from rest with an acceleration $a_2$. If they travel equal distance in the $5^{th} \ s$ after the start of $A$,then the ratio $a_1 : a_2$ is equal to

When two species of different genealogy come to resemble each other as a result of adaptation,the phenomenon is termed as

While a collector to emitter voltage is constant in a transistor,the collector current changes by $8.2 ~mA$ when the emitter current changes by $8.3 ~mA$. The value of forward current ratio is

Phytochrome is involved in:

If the circle $x^2+y^2+8x-4y+c=0$ touches the circle $x^2+y^2+2x+4y-11=0$ externally and cuts the circle $x^2+y^2-6x+8y+k=0$ orthogonally,then $k=$