$A$ marine cartilaginous fish that can produce electric current is

If a set $A$ has $n$ elements,then the total number of subsets of $A$ is:

If an electron in a hydrogen atom jumps from the $3^{\text{rd}}$ orbit to the $2^{\text{nd}}$ orbit,it emits a photon of wavelength $\lambda$. When it jumps from the $4^{\text{th}}$ orbit to the $3^{\text{rd}}$ orbit,the corresponding wavelength of the photon will be

In an experiment with $15$ observations on $x$,the following results were available: $\sum x^2 = 2830$ and $\sum x = 170$. One observation that was $20$ was found to be wrong and was replaced by the correct value $30$. Then the corrected variance is:

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

The more commonly used baking powder contains about $30 \% NaHCO_3, 20 \% NaAl(SO_4)_2, 10 \% Ca(H_2PO_4)_2$ and $40 \% $ starch. Which of the following statements is/are correct?