Mrs. Simons said that only 29 percent of the earth consisted of land.


If the subordinate clause states a universal truth, it assumes a present tense. ‘Consisted’ is past tense.
The correct sentence is, ‘ Mrs. Simon said that only 29 percent of the earth consists of land’.



The soldiers said that they will be ready for the attack.

If the main clause is stated in the past tense, the following subordinate clause assumes a conditional past tense. ‘Will be’ is future tense which has to be turned into a conditional ‘would be’.
The correct sentence is ‘The soldiers said that they would be ready for the attack’.




I study hard so that I scored good grades.


A sentence wherein the subordinate clause indicates purpose, if the main clause is stated in present or future tense, the subordinate clause assumes a present tense. Here, the purpose is to score good grades.
Hence the correct sentence is, ‘I study hard so that I may score good grades’.


The teacher said that she is happy with Sam’s results.


If the main clause is stated in the past tense, the following subordinate clause also assumes a past tense. ‘Is’ is simple present tense which has to be turned into past tense ‘was’.
The correct sentence is, ‘The teacher said that she was happy with Sam’s results’.