81.Which of the following types of woods is specially used as railways sleepers ?

82.The study of the interaction of antigens and antibodies is called :

83.Which of the following is/are true about stereoscopic vision ? 1. It gives a three-dimensional effect to the object observed 2. It helps one to judge distance3. It is well-developed in birds and animals with eyes in the sides of their heads

84.Which of the following diseases usually spreads through milk ?

85.Pregnant women usually become deficient in