Study the following and choose the correct statements:
I. If a single gene influences more than one phenotypic trait, it is called pleiotropy.
II. Due to absence of antibodies anti A and anti B, the persons with AB blood group are described as universal recipients.
III. Inheritance of sex-linked dominant traits follows criss-cross inheritance.
IV. If sex index ratio is 0.33, then sexual phenotype of Drosophila is intersex.