Which of the following is an incorrect combination?

How many of the given statements $(i-iv)$ is/are correct?
$i.$ In transcription,adenosine pairs with uracil.
$ii.$ Regulation of lac operon by repressor is referred to as positive regulation.
$iii.$ The human genome has approximately $50,000$ genes.
$iv.$ Haemophilia is a sex-linked recessive disease.

What do genes control?

In Lederberg's replica plating experiment,what should be used to obtain streptomycin-resistant strains?

Which of the following is used as a screening agent in the replica plating experiment?

Select the correct statement from the following.