Which from the following dopants is used in germanium to produce $p-$type semiconductor?

The conductivity of semiconductors $..........$ with an increase in temperature.

Which pair is not isomorphous?

Select the correct statements.
$(A)$ Crystalline solids have long range order.
$(B)$ Crystalline solids are isotropic.
$(C)$ Amorphous solids are sometimes called pseudo solids.
$(D)$ Amorphous solids soften over a range of temperature.
$(E)$ Amorphous solids have a definite heat of fusion.
Choose the most appropriate answer from the options given below:

Which one of the following is used as a piezoelectric material?

To get an $n-$type semiconductor,the impurity to be added to silicon should have which of the following number of valence electrons?