Answer: Option (4)
Explanation: In order to be a theory, a hypothesis or a model has to be able to prove the required necessary conditions and also it should be explainable.
The observations that were made initially, by studying about Venus was not sufficient enough to consider it to be a theory. Some additional evidences must be put forward in support of the observation. In doing this, different data are obtained which may sometime show error, leading to the failure of the experiment. So the evidences and the experiments must be correct enough to get the correct data.
It cannot considered to be a theory by making just a few observations. In the recent years, a lot of experiments, tests has been carried out regarding Venus and therefore were able to prove it as theory.
Thus, the correct answer is option (4).