the ground beneath the Nelson's house is beginning to Sag and sink which of the following is a possible explanation the ground has been exhausted, the Nelson's have built there home on a continental plate, there is too much salt in the soil, or leaching is causing the soul to weaken

There's to much salt in the soil

Option: (D) -

Due to the process of leaching the soil is weakened which some how causes the unfortunate events more rarely in some regions.

Explanation:

Evaluating other options:

Tectonic plates will never effect a single house, as for the ground exhaustion there is also minimal possibility for that.

The process of Leaching:

The flow of water is always uninterrupted and as it does not move all by itself as it also carry some soluble elements. Now, these water molecules come all the way from the rivers and oceans and from high hills down to lower grounds. As due that the ground is weekend and many unfortunate may be faced by the local residents.