In this task, you are given a question and a context passage. You have to answer the question based on the given passage.

What is sometimes combined with an RPG tube to keep from harming the user?, Context: Rocket-propelled grenades can be—and often are—used against hovering helicopters (e.g., by Somali militiamen during the Battle of Mogadishu (1993)). Firing an RPG at steep angles poses a danger to the user, because the backblast from firing reflects off the ground. In Somalia, militia members sometimes welded a steel plate in the exhaust end of an RPG's tube to deflect pressure away from the shooter when shooting up at US helicopters. RPGs are used in this role only when more effective weapons are not available.
a steel plate in the exhaust end

what has the better chloroplasts, Context: The alga Cyanophora, a glaucophyte, is thought to be one of the first organisms to contain a chloroplast. The glaucophyte chloroplast group is the smallest of the three primary chloroplast lineages, being found in only 13 species, and is thought to be the one that branched off the earliest. Glaucophytes have chloroplasts that retain a peptidoglycan wall between their double membranes, like their cyanobacterial parent. For this reason, glaucophyte chloroplasts are also known as muroplasts. Glaucophyte chloroplasts also contain concentric unstacked thylakoids, which surround a carboxysome - an icosahedral structure that glaucophyte chloroplasts and cyanobacteria keep their carbon fixation enzyme rubisco in. The starch that they synthesize collects outside the chloroplast. Like cyanobacteria, glaucophyte chloroplast thylakoids are studded with light collecting structures called phycobilisomes. For these reasons, glaucophyte chloroplasts are considered a primitive intermediate between cyanobacteria and the more evolved chloroplasts in red algae and plants.
red algae

What are the conditions under which a state can pull out of its treaty obligations?, Context: Treaties are not necessarily permanently binding upon the signatory parties. As obligations in international law are traditionally viewed as arising only from the consent of states, many treaties expressly allow a state to withdraw as long as it follows certain procedures of notification. For example, the Single Convention on Narcotic Drugs provides that the treaty will terminate if, as a result of denunciations, the number of parties falls below 40. Many treaties expressly forbid withdrawal. Article 56 of the Vienna Convention on the Law of Treaties provides that where a treaty is silent over whether or not it can be denounced there is a rebuttable presumption that it cannot be unilaterally denounced unless:

as long as it follows certain procedures of notification