Questions

A seconds pendulum is a pendulum whose period is precisely two seconds i.e, one second for a swing in one direction and one second for the return swing.

The lymphatic system is a complex system of fluid drainage and transport, and immune response and disease resistance. Fluid that is forced out of the bloodstream during normal circulation is filtered through lymph nodes to remove bacteria, abnormal cells and other matter. This fluid is then transported back into the bloodstream via the lymph vessels. Lymph only moves in one direction, toward the heart.

The Aortic valve - located between the left ventricle and the aorta

The Mitral valve - located between the left atrium and left ventricle

The Tricuspid valve - located between the right atrium and the right ventricle (and) 

The Pulmonary (pulmonic) valve - located between the right ventricle and the pulmonary artery.

German Silver is an alloy of copper, nickel and zinc. It is composed of 60% copper, 20% nickel and 20% zinc. Due to its white-silverish appearance it is named as german silver but it contains no silver in it.

The American Civil War (1863)

A sponge has many holes but it absorbs water and can hold them in it.