Identify the correct statement about plant water relations: MCQ with Answer and Explanation

Explanation:
Ascariasis is a helminthic infection caused by the intestinal roundworm Ascaris lumbricoides. Ringworm (dermatophytosis) is a superficial fungal infection of the skin, hair, or nails caused by dermatophytes like Microsporum. Amoebiasis is an intestinal infection caused by the protozoan parasite Entamoeba histolytica, not a bacterium. Thus, statements 1 and 2 are correct.

Explanation:
The lac operon in E. coli is a classic example of an inducible operon. It is normally 'off' (repressed) because the lac repressor protein, produced by the 'i' gene, binds to the operator, preventing transcription of the structural genes (z, y, a) needed for lactose metabolism. However, when lactose is present in the environment, it is converted to allolactose, which acts as an inducer. Allolactose binds to the repressor, changing its shape and preventing it from binding to the operator, thus 'inducing' or allowing transcription to occur.

Explanation:
Natural passive immunity occurs when pre-formed antibodies are transferred naturally from one individual to another. During pregnancy, maternal antibodies (primarily IgG) cross the placenta to the fetus, providing temporary protection against diseases the mother is immune to. Colostrum (mother's milk) also provides IgA antibodies to the newborn.