Problem: Myocardial infarction:

The main treatment for MI with ECG evidence of ST elevation (STEMI) include thrombolysis and percutaneous coronary intervention. Primary percutaneous coronary intervention (PCI) is the treatment of choice for STEMI if it can be performed in a timely manner. If PCI cannot be performed within 90 to 120 minutes then thrombolysis, preferably within 30 minutes of arrival to hospital, is recommended. If a person has had symptoms for 12 to 24 hours evidence for thrombolysis is less and if they have had symptoms for more than 24 hours it is not recommended.

When must ECG evidence be taken?
---
A: unanswerable


Problem: Biodiversity:

Habitat size and numbers of species are systematically related. Physically larger species and those living at lower latitudes or in forests or oceans are more sensitive to reduction in habitat area. Conversion to "trivial" standardized ecosystems (e.g., monoculture following deforestation) effectively destroys habitat for the more diverse species that preceded the conversion. In some countries lack of property rights or lax law/regulatory enforcement necessarily leads to biodiversity loss (degradation costs having to be supported by the community).[citation needed]

What is systematically related to the numbers of species?
---
A: Habitat size


Problem: Immunology:

In the mid-1950s, Frank Burnet, inspired by a suggestion made by Niels Jerne, formulated the clonal selection theory (CST) of immunity. On the basis of CST, Burnet developed a theory of how an immune response is triggered according to the self/nonself distinction: "self" constituents (constituents of the body) do not trigger destructive immune responses, while "nonself" entities (e.g., pathogens, an allograft) trigger a destructive immune response. The theory was later modified to reflect new discoveries regarding histocompatibility or the complex "two-signal" activation of T cells. The self/nonself theory of immunity and the self/nonself vocabulary have been criticized, but remain very influential.

What triggers an immune response according to CST?
---
A: self/nonself distinction


Problem: Nanjing:

A monument to the huge human cost of some of the gigantic construction projects of the early Ming dynasty is the Yangshan Quarry (located some 15–20 km (9–12 mi) east of the walled city and Ming Xiaoling mausoleum), where a gigantic stele, cut on the orders of the Yongle Emperor, lies abandoned, just as it was left 600 years ago when it was understood it was impossible to move or complete it.

Why was the stele abandoned?
---
A:
it was impossible to move or complete it