Which of the following arrangements shows the schematic alignment of magnetic moments of an antiferromagnetic substance?

Which type of impurity is added to form a $p$-type semiconductor?

$MnO$ is $:$

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:

Quartz is a crystalline variety of

The one that is extensively used as a piezoelectric material is