Explain why all models have limitations

All models have limitations because they are not representative of every possible scenario. They use current knowledge and scientific data, but as those are subject to change, the models based off that knowledge and data are subject to change as well.

Explanation:

the answer is either c or d i think its d

productive most commonly means: achieving or producing a significant amount or result.

explanation:

productive can also mean:

these depend on how the word productive is used. most likely productive will mean   achieving or producing a significant amount or result.