Ancient astronomers thought that earth was flat. which observation eventually proved that this is wrong? a) earth is at the center of the solar system. b) the moon and the sun are spherical in shape. c) there are days and nights and seasons on earth. d) earth’s shadow on the moon shows it is spherical.

D) Earth's shadow on the moon shows it is spherical.

Explanation:

According to ancient astronomers, Earth was flat. But it was eventually proved wrong.

1. Had Earth been flat, ship in the sea could be seen for a far distance but it is not so.

2. During the lunar eclipse, the shadow of the Earth falling on moon would have been flat or would have sharp edges. But, the shadow was found to be round in shape. A spherical object casts a round shadow.

Thus, option D is correct.

white blood cells or wbc s are mainly 2 types-

1.agranulocytes

2.granulocytes

the monocytes or macrophages of agranulocytes , dendritic cells which are accessory leucocytes, and b cells which is one type of lymphocytes   identify the antigens present on the pathogen's surface. these three cells are called antigen presenting cells(apc) which are phagocytes and destroy the antigens by secreting antitoxins. besides this leukocyte is always plays vital role in the immunity of the body.