Which of the following are mixed oxides:

The correct option is D Pervoskite
Three important mixed oxide structures exist: spinel, perovskite, and ilmenite.

Spinel: The spinels have the general formula $A{B}_2{O}_4$. Generally, $A$ is a divalent ion, $A^{2+}$, and $B$ is trivalent, $B^{3+}$. The structure can be described as being based on a cubic close-packed array of oxide ions, with $A^{2+}$ ions occupying tetrahedral holes and $B^{3+}$ ions occupying octahedral holes. $A$ spinel crystal containing $nA{B}_2{O}_4$ formula units has $8n$ tetrahedral holes and $4n$ octahedral holes; accordingly, one-eighth of the tetrahedral holes are occupied by $A^{2+}$ ions and one-half of the octahedral holes by the $B^{3+}$ ions.

Pervoskite: This structure is named after the mineral $CaTi{O}_3$. A unit cell is shown. This unit cell is known as the $A$-type because if we take the general formula $AB{X}_3$ for the perovskites, then the $A$ atom is at the centre in this cell. The central $Ca\left(A\right)$ atom is coordinated to $8Ti$ atoms $\left(B\right)$ at the corners and to $12$ oxygens $\left(X\right)$ at the midpoints of the cell edges. The structure can be usefully described in other ways. First, it can be described as a ccp array of $A$ and $X$ atoms with the $B$ atoms occupying the octahedral holes. Second, perovskite has the same octahedral framework as $Re{O}_3$ based on $B{X}_6$ octahedral with an $A$ atom added in at the centre of the cell. Compounds adopting this structure include $SrTi{O}_3,SrZr{O}_3,SrHf{O}_3,SrSn{O}_3,$ and $BaSn{O}_3$. The structures of the high temperature superconductors are based on this structure.


The Ilmenite Structure:
The ilmenite structure is adopted by oxides of formula $AB{O}_3$ when $A$ and $B$ are similar in size and their total charge adds up to $+6$. The structure is named after the mineral of $F{e}^{II}T{i}^{IV}{O}_3$, an hcp array of oxygens, but now two different cations are present occupying two-thirds of the octahedral holes.