What is the difference between a heterogeneous mixture and a homogeneous mixture?

question 4 options:

a heterogeneous mixture is a pure substance and a homogeneous mixture is not.

a heterogeneous mixture has particles that are not uniformly distributed, but a homogeneous mixture has particles that are uniformly distributed.

a homogeneous mixture is a pure substance and a heterogeneous mixture is not.

a homogeneous mixture has particles that are not uniformly distributed, but a heterogeneous mixture has particles that are uniformly distributed.

A heterogeneous mixture has particles that are not uniformly distributed, but a homogeneous mixture has particles that are uniformly distributed.

Mantle convection  is the slow  creepingmotion of earth's solid silicate  mantle  caused by  convection  currents carrying  heat from the interior  to the planet's surface.[1][2]  the earth's surface  lithosphere, which rides atop the  asthenosphere  (the two components of the  upper mantle), is divided into a number of  plates  that are continuously being created and consumed at their opposite  plate boundaries. accretion occurs as mantle is added to the growing edges of a plate, associated with  seafloor spreading. this hot added material cools down by  conduction  and  convection  of heat. at the consumption edges of the plate, the material has thermally contracted to become dense, and it sinks under its own weight in the process of  subduction  usually at an  ocean trench.[3]this subducted material sinks through the earth's interior. some subducted material appears to reach the lower mantle,[4]  while in other regions, this material is impeded from sinking further, possibly due to a phase transition from  spinel  to  silicate perovskiteand  magnesiowustite, an  endothermic reaction.[5]the subducted oceanic crust triggers  volcanism, although the basic mechanisms are varied. volcanism may occur due to processes that add buoyancy to partially melted mantle causing an upward flow due to a decrease in density of the partial melt.secondary forms of convection that may result in surface volcanism are postulated to occur as a consequence of intraplate extension[6]  and  mantle plumes.[7]it is because the mantle can convect that the  tectonic plates  are able to move around the earth's surface.[8]mantle convection seems to have been much more active during the  hadean  period, resulting in gravitational sorting of heavier molten  iron, and  nickel  elements and  sulphides  in the core, and lighter  silicate minerals  in the  mantle.

In order to understand the problems of unwanted infertility in a country — the gambia — where the desire for children and the fertility is very high, a population-based survey was undertaken. all infertile women in 24 randomly selected enumeration areas were assessed. the study included a review of the problems faced and coping mechanisms employed by infertility clients and types of health care available for infertile couples in the different types and levels of the formal and traditional health system. half of the infertile couples failed to seek formal health care, and they have to reach a certain level of care in order to be properly managed. alternative care is often sought. child fostering is also a frequent solution to childlessness. in-depth interviews revealed that traditional care like healers and spiritual leaders are frequently consulted long before formal health care. this delay could be a problem in those cases where infertility is caused by infections.