If the points \(( a 1, b 1),( a 2, b 2)\) and \(( a 1+ a 2, b 1+ b 2)\) are collinear, then

The general solution of the differential equation \(\frac{d y}{d x}+4 x y^2=0\) is :

If the matrix \(\left(\begin{array}{ccc}2 & 4 & 5 \\ 4 & 2 & 3 \\ K & 3 & 2\end{array}\right)\) is a symmetric matrix, then the value of \(K\) is :

If \(C(x)=a x^ 2-bx-c\) represents the total cost function then the slope of the tangent to the marginal cost curve at the point \((x, y)\) is:

Using integration the area enclosed by the ellipse \(\frac{x^2}{a^2}+\frac{y^2}{b^2}=1\) is equal to :

Area of the region bounded by \(y=x^2\) and the line \(y=16\) is

The corner points of the bounded feasible region determined by the system of linear inequalities are (0, 0), (4, 0), (2, 4) and (0, 5). If maximum value of z = ax + by, where a, b > 0 occurs at both (2, 4) and (4, 0) then

An unbiased coin is tossed 6 times. The Probability of getting at least one head is:

The interval in which \(f(x)=\sin x-\cos x, 0 \leq x \leq 2 \pi\) is strictly decreasing is:

Which one of the following is not an example of narrowly utilitarian reason to conserve biodiversity?

Two circular coils of diameter 10 cm and 20 cm, carrying equal currents have the same number of turns. The ratio of magnetic fields produced at the center of coils, respectively will be

Read the following passage carefully and answer the given questions.
Immune System in the Body
The human immune system consists of lymphoid organs, tissues, cells and soluble molecules like antibodies. The primary lymphoid organs are bone marrow and thymus where immature lymphocytes differentiate into antigen-sensitive lymphocytes. After maturation the lymphocytes migrate to secondary lymphoid organs like spleen, lymph nodes, tonsils, Peyer's patches of small intestine and appendix. The secondary lymphoid organs provide the sites for interaction of lymphocytes with the antigen, which then proliferate to become effector cells. The bone marrow is the main lymphoid organ where all blood cells including lymphocytes are produced. Each antibody molecule has four peptide chains, two small called light chains and two longer called heavy chains. Hence, an antibody is represented as H2L2. Different types of antibodies are produced in our body. IgA, IgM, IgE, IgG are some of them. Techniques like radiography (use of X-rays), CT (computed tomography) and MRI (magnetic resonance imaging) are very useful to detect cancers of the internal organs.
The site of interaction of lymphocytes with antigen is

The step 'D' in the figure depicts: