Which of the following is not a Lewis acid?

The $\pi$-acid ligand which uses its $d$-orbital during synergic bonding in its complex compound is

Somatic hybrids are produced by

The sum of the first four terms of an arithmetic progression is $56$ and the sum of its last four terms is $112$. If the first term is $11$,what is the number of terms in the progression?

Let $A$ and $B$ be independent events with $P(A)=0.3$ and $P(B)=0.4$. Find $P(A | B)$.

Radius of gyration of a body depends on