Which one of the following is wrong for fungi?

Which of the following statements is not correct?

$A$ student connects a long air-cored coil of manganin wire to a $100\,V$ $D.C.$ supply and records a current of $25\,A$. When the same coil is connected across a $100\,V$,$50\,Hz$ $A.C.$ supply,the current reduces to $20\,A$. The reactance of the coil is....$\Omega $

$A$ beam of light of wavelength $600\, nm$ from a distant source falls on a single slit $1\, mm$ wide and the resulting diffraction pattern is observed on a screen $2\, m$ away. The distance between the first dark fringes on either side of the central bright fringe is

Which of the following is the most stable ecosystem?

Two unknown resistances are connected in two gaps of a meter-bridge. The null point is obtained at $40 \ cm$ from left end. A $30 \Omega$ resistance is connected in series with the smaller of the two resistances, the null point shifts by $20 \ cm$ to the right end. The value of smaller resistance in $\Omega$ is