Expansion joints in masonry walls are provided if length exceeds A. 10 m B. 20 m C. 30 m D. 40 m E. 50 m.

If we omit environmental factors like temperature, seismic etc. and local regulations for each country and use standart conditions then EJ for brick wall to be preferable located at every30-40 m distance. The distance between EJ for brick wall will be longer than for reinforced concrete which will be recommended to have EJ every20-25m. This is because brick wall has much less thermal expansion coefficients (due to multiple mini joints between each block, mortar and materials properties) than concrete wall. So, the answer D is the best option.

Though the Ques. relates to Civil Design however, as per our observation in construction field, I would go for Option "A" /10 Meters.

Thanks  En.Alex

choose "20-30" as usual in my country... 

(A) is the nearest answer, but some detailing is important :

If the wall is veneer (without reinforcement) then the length will be from7-10 m for clay brick and5-7 m for concrete brick

If the wall is reinforced the expansion joint will be applied every15 m.

 

Expansion joints in masonry walls are provided if length exceeds "40 m". So choice "D" is the correct answer

I think that there was missing data 

For boundary walls wich built from brick  , the suitable joint length15 m , and for partitions or bearing walls the suitable joint length (30-45 m) 

We must not forget the Differing standards between countries due to differences in climate and the contrast in temperatures.

I believe the correct answer is D-40 m, however I have to agree with Mr.Kinsbergen..., it can variate depending on the design and on the code of the country the structure is build if not ISO is used. India has30 m  

Expansion joints in masonry walls are provided when length exceeds 40 m.

D.40 m.

Expansion joint will act as a resultant effect for every A) 10 meters

Expansion joints are provided in the masonary walls when length of the wall exceeds20 to25 meter.

Sorry I always have more questions about a question, but depending on windows, doors and other boundaries it can be6 or7 meters, for large walls it can be30 to40 meters. So no straight answer, depending on the design,