''$A$ perfect black body is black in colour.'' Is this statement true or false?

For an opaque body,the coefficient of transmission is:

Nearly $10 \%$ of the power of a $110\,W$ light bulb is converted to visible radiation. The change in average intensities of visible radiation,at a distance of $1\,m$ from the bulb to a distance of $5\,m$ is $a \times 10^{-2}\,W/m^2$. The value of '$a$' will be.

If the absorption and reflection coefficients of a surface of a body are $0.4$ and $0.6$ respectively,then

If a black body at $400 \ K$ surrounded by atmosphere at $300 \ K$ has a rate of cooling '$R_0$',the same body at $900 \ K$,surrounded by the same atmosphere,will have a rate of cooling nearly:

What would happen if the greenhouse effect were not present?