Consider two circuits, (A) and (B), each having two resistors. One of them has a positive temperature coefficient of resistance, +$\alpha$, while the other one has a negative temperature of coefficient, -$\alpha$, as shown in the figure. The current through these circuits are denoted by $I_{A}$ and $I_{B}$. At initial temperature, the resistance of the two resistors is $R_0$. As the temperature is increased, the correct option that describes the variation of current in these circuits is:

Sponges exchange $O_{2}$ with $CO_{2}$ by

Cell theory was formulated by

Consider the following nuclear reaction ${}^{238}U\longrightarrow{}^{234}Th+{}^{4}He$. Take masses of ${}^{238}U$, ${}^{234}Th$ and ${}^{4}He$ as 238.050 u, 234.043 u and 4.003 u, respectively. The Q value for the reaction, in keV, is: [Given: $1~u=931.5~MeV~c^{-2}$]

Given below are two statements: Statement I: Modern Homo sapiens arose in Australia and moved across continents. Statement II: Homo sapiens arose around 75000 to 10000 years ago. In the light of the above statements, choose the most appropriate answer from the options given below: