In this question, we are asked to identify the elements that can have a valency of two within the carbon family. The carbon family consists of carbon, silicon, germanium, tin, and lead.

A valency refers to the combining capacity of an atom, or the number of electrons an atom needs to gain, lose, or share to achieve a stable electron configuration. In the case of the carbon family, the common valency for all the elements is four. This means that each of these elements typically forms compounds by sharing or gaining/losing four electrons.

However, the question states that some elements in the carbon family can have a valency of two as well. From the options provided, option 1 includes silicon, germanium, and tin, which are all part of the carbon family. These three elements can indeed have a valency of two in certain compounds. Therefore, option 1 is a correct response.

Option 2 suggests that only germanium and tin can have a valency of two. This is incorrect because silicon, another element in the carbon family, can also have a valency of two. Therefore, option 2 is not the correct answer.

Option 3 states that germanium, tin, and lead can have a valency of two