Match the defects in Group 1 with possible causes in Group 2.

Group 1	Group 2
P. Misruns	1. Sand expansion
Q. Shifts	2. Molding materials
R. Blowholes	3. Improper heating of metals
S. Scabs	4. Molding and core making

Why the quality of sand deteriorates if the same molding sand is used again and again?

A. Build up of clay and other organic coatings on the molding sand particles

B. Presence of foreign and scrap matter like iron particles, feyalite, etc.

C. Occurrence of pieces of oil sand

D. All of these

Shrinkage allowances is also known as

A. finish allowance

B. contraction allowance

C. taper allowance

D. camber allowance

Green sand consists of

A. 70% sand and 30% clay

B. 40% sand and 60% clay

C. 30% sand and 70% clay

D. 60% sand and 40% clay

The low permeability in sand can cause which of the following defects in casting

A. Rough surface

B. Blow holes

C. hot tears

D. Drop