Which crystal system has no axis of rotation of symmetry?

$a \ne b \ne c$,$\alpha \ne \beta \ne \gamma \ne 90^{\circ}$ represent:

Which of the following represents the correct axial distances and axial angles for the rhombohedral crystal system?

What is the relationship between the axial angles in an orthorhombic crystal system?

Chromium metal crystallises in a body-centred cubic $(bcc)$ lattice. The edge length of the unit cell is found to be $287 \, pm$. The atomic radius of chromium will be ............. $pm$.

The triclinic unit cell has the following parameters: