Which one of the following gives a sooty flame on combustion?

Three rods of equal lengths are joined to form an equilateral triangle $ABC$. $D$ is the mid-point of $AB$. The coefficient of linear expansion is $\alpha_1$ for the material of rod $AB$ and $\alpha_2$ for the material of rods $AC$ and $BC$. If the distance $DC$ remains constant for small changes in temperature,then

Ground tissue includes

$A$ motor boat is travelling with a speed of $3.0 \, m/s$. If the force on it due to water flow is $500 \, N$,the power of the boat is:

$A$ string of length $L$ is fixed at one end and carries a mass $M$ at the other end. The string makes $2/\pi$ revolutions per second around the vertical axis through the fixed end as shown in the figure,then the tension in the string is:

What is the cell wall of Protista composed of?