In the concentration of $PbS$ containing $ZnS$ as impurity,the depressant used is:

If $x=\log _{0.1} 0.001$ and $y=\log _9 81$,then $\sqrt{x-2 \sqrt{y}}$ is equal to

The output characteristics of an $n-p-n$ transistor represent,($I_C=$ collector current,$V_{C E}=$ potential difference between collector and emitter,$I_B=$ base current,$V_{B B}=$ voltage given to base,$V_{B E}=$ the potential difference between base and emitter)

$A$ 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

Amongst the given taxonomic aids,how many are associated with the preservation of specimens? Monograph,Flora,Key,Museums,Botanical Gardens,Catalogue,Herbarium,Manual

The second and third rows of transition elements resemble each other much more than they resemble the first row. Explain why?