The correct answer choice is E, you are correct about that. However, I am not sure I fully understand your question regarding the use of instruments? Are you asking how we could detect continental drift with the use of new instruments? If this is the case, then I have two notes for you moving forward.
First, if a non-central idea such as this comes up, it is not necessary for you to know the methods they employed to detect continental drift, nor how they work. If they tell you that new instruments were able to detect this, then it is best to simply accept and move forward. There will not be any questions on the LSAT that will test your outside knowledge of what they used or how they managed to measure this.
Secondly, if it does help you to imagine something more concrete rather than "instruments", you can substitute the idea word instruments with "possibly satellite imaging" or whichever other tools you'd imagine that we could use to measure the movement of continents. This would simply be to help you become more familiar with the argument and improve your understanding.
The main takeaway is not to be swayed by these distracting elements of the passages. I hope this is what you were asking about, if not, please do ask again and I will make sure to respond!